I just installed the latest build of Debian Squeeze. When kdm displays the login screen my USB-connected keyboard and mouse don't react. When I then unplug and re-attach them everything ist fine. Surely this can't be working as intended? I can however get into BIOS-Setup as usual during the initial boot-phase by pressing Crtl-S and F1. I have played around with the legacy support for mouse/keyboard - to no avail. Any hints would be highly appreciated.

This certainly seems like an Xorg configuration issue. I suggest checking /etc/X11/xorg.conf and /etc/X11/xorg.conf.d/

Thanks for your prompt answer. For one thing, there is no xorg.conf anywhere on my system (Debian Squeeze). As suggested after some Google research, I tried to run Xorg -configure just to see what it would generate as an xorg.conf. But I got the following reply...
Xorg -configure > /etc/xorg.conf.new

Fatal server error:
Server is already active for display 0
If this server is no longer running, remove /tmp/.X0-lock
and start again.


Please consult the The X.Org Foundation support
at http://wiki.x.org
for help.
I suppose one can only run Xorg -configure when the XServer isn't active.
Maybe I just better wait a bit, since I am of course using a Debian distro which is still at the "testing" stage.
Regards

You will need to stop KDM in order to run Xorg -configure

I ran Xorg -configure --- >> no change. Mouse and keyboard are o.k. during bios time, but when the login-dialog box appears I cannot use them until I re-attach the USB-connection.

Can you use a remote terminal or some other method ( such as timed script ) to capture the output of "xinput -list" before and after the disconnection?

Hello, I haven't dived into Debian enough to quickly implement your suggestion. However, I am enclosing the kern.log of the last boot below (don't know how to attach files!). In that I can see that on line 530 ist says
New USB device found, idVendor=046d, idProduct=c03e (address: 5; optical Logitech mouse) and then on line 542
New USB device found, idVendor=046d, idProduct=c31c (address: 6; keyboard).
It seems to get "interesting again on line 632 etc. with the message
usb 2-1.8: USB disconnect, address 6.
I wonder whether you can make anything of that?
Regards from Salzburg and many thanks for your help.
-------------------------------------
2.754607] usb 2-1.5: new full speed USB device using ehci_hcd and address 4
2.855589] usb 2-1.5: New USB device found, idVendor=046d, idProduct=0a0c
2.855594] usb 2-1.5: New USB device strings: Mfr=1, Product=2, SerialNumber=0
2.855598] usb 2-1.5: Product: Logitech USB Headset
2.855601] usb 2-1.5: Manufacturer: Logitech
2.855680] usb 2-1.5: configuration #1 chosen from 1 choice
2.929662] usb 2-1.7: new low speed USB device using ehci_hcd and address 5
3.035014] usb 2-1.7: New USB device found, idVendor=046d, idProduct=c03e
3.035019] usb 2-1.7: New USB device strings: Mfr=1, Product=2, SerialNumber=0
3.035023] usb 2-1.7: Product: USB-PS/2 Optical Mouse
3.035026] usb 2-1.7: Manufacturer: Logitech
3.035092] usb 2-1.7: configuration #1 chosen from 1 choice
3.109714] usb 2-1.8: new low speed USB device using ehci_hcd and address 6
3.210203] usb 2-1.8: New USB device found, idVendor=046d, idProduct=c31c
3.210209] usb 2-1.8: New USB device strings: Mfr=1, Product=2, SerialNumber=0
3.210213] usb 2-1.8: Product: USB Keyboard
3.210216] usb 2-1.8: Manufacturer: Logitech
3.210295] usb 2-1.8: configuration #1 chosen from 1 choice
.....
3.771285] input: Logitech USB-PS/2 Optical Mouse as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.7/2-1.7:1.0/input/input4
3.771326] generic-usb 0003:046D:C03E.0002: input,hidraw1: USB HID v1.10 Mouse [Logitech USB-PS/2 Optical Mouse] on usb-0000:00:1d.0-1.7/input0
3.774060] input: Logitech USB Keyboard as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.8/2-1.8:1.0/input/input5
3.774098] generic-usb 0003:046D:C31C.0003: input,hidraw2: USB HID v1.10 Keyboard [Logitech USB Keyboard] on usb-0000:00:1d.0-1.8/input0
3.780992] input: Logitech USB Keyboard as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.8/2-1.8:1.1/input/input6
3.781024] generic-usb 0003:046D:C31C.0004: input,hidraw3: USB HID v1.10 Device [Logitech USB Keyboard] on usb-0000:00:1d.0-1.8/input1
3.781034] usbcore: registered new interface driver usbhid
3.781036] usbhid: v2.6:USB HID core driver
.....
19.705159] eth0: no IPv6 routers present
80.847793] usb 2-1.8: USB disconnect, address 6
81.140962] usb 2-1.8: new low speed USB device using ehci_hcd and address 8
81.238206] usb 2-1.8: New USB device found, idVendor=046d, idProduct=c31c
81.238210] usb 2-1.8: New USB device strings: Mfr=1, Product=2, SerialNumber=0
81.238213] usb 2-1.8: Product: USB Keyboard
81.238216] usb 2-1.8: Manufacturer: Logitech
81.238301] usb 2-1.8: configuration #1 chosen from 1 choice
81.243549] input: Logitech USB Keyboard as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.8/2-1.8:1.0/input/input9
81.243708] generic-usb 0003:046D:C31C.0005: input,hidraw2: USB HID v1.10 Keyboard [Logitech USB Keyboard] on usb-0000:00:1d.0-1.8/input0
81.250897] input: Logitech USB Keyboard as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.8/2-1.8:1.1/input/input10
81.251008] generic-usb 0003:046D:C31C.0006: input,hidraw3: USB HID v1.10 Device [Logitech USB Keyboard] on usb-0000:00:1d.0-1.8/input1
87.997873] usb 2-1.8: USB disconnect, address 8
96.112800] usb 2-1.8: new low speed USB device using ehci_hcd and address 9
96.210434] usb 2-1.8: New USB device found, idVendor=046d, idProduct=c31c
96.210438] usb 2-1.8: New USB device strings: Mfr=1, Product=2, SerialNumber=0
96.210442] usb 2-1.8: Product: USB Keyboard
96.210444] usb 2-1.8: Manufacturer: Logitech
96.210538] usb 2-1.8: configuration #1 chosen from 1 choice
96.216071] input: Logitech USB Keyboard as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.8/2-1.8:1.0/input/input11
96.216228] generic-usb 0003:046D:C31C.0007: input,hidraw2: USB HID v1.10 Keyboard [Logitech USB Keyboard] on usb-0000:00:1d.0-1.8/input0
96.223356] input: Logitech USB Keyboard as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.8/2-1.8:1.1/input/input12
96.223434] generic-usb 0003:046D:C31C.0008: input,hidraw3: USB HID v1.10 Device [Logitech USB Keyboard] on usb-0000:00:1d.0-1.8/input1
97.191088] usb 2-1.7: USB disconnect, address 5
97.900586] usb 2-1.7: new low speed USB device using ehci_hcd and address 10
97.998198] usb 2-1.7: New USB device found, idVendor=046d, idProduct=c03e
97.998203] usb 2-1.7: New USB device strings: Mfr=1, Product=2, SerialNumber=0
97.998207] usb 2-1.7: Product: USB-PS/2 Optical Mouse
97.998210] usb 2-1.7: Manufacturer: Logitech
97.998314] usb 2-1.7: configuration #1 chosen from 1 choice
98.001396] input: Logitech USB-PS/2 Optical Mouse as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.7/2-1.7:1.0/input/input13
98.001569] generic-usb 0003:046D:C03E.0009: input,hidraw1: USB HID v1.10 Mouse [Logitech USB-PS/2 Optical Mouse] on usb-0000:00:1d.0-1.7/input0
----------------------------------------------------

Hello again, I really am not up to completely understanding USB. Could it be that the problem might be a consequence of mixing USB levels (USB 1 and USB 2). Maybe the addresses used to start with (5 and 6 respectively) might be "overlayed" or used for something else. De- and re-attaching apparently then uses addresses 9 and 10. But, then I might just be talking out of the back of my head...

I could send you a copy of the complete kern.log, if that might help...

I'm using kubuntu. Sometimes my USB keybord doesn't work with kdm. All I have to do is to remove it and insert it into an other slot...

Good morning! The same here - kind of! I only have to pull the keyboard's/mouse's attachment out of the USB-socket and then re-insert them into the same place for everything to work afterwards. As you can see from the kern.log I included in my last message, new addresses are used afterwards, however.