Not sure if anyone can help me on this, but I'm pretty sure is Amarok...

So the issue:

Kubuntu 10.10 64bit, fully updated, with Kde 4.6 and Amarok 2.4.0

On start/restart/reboot if Amarok auto-starts after login, then I have the following error message:

Message-did-not-receive-a-reply-timeout-by-message-bus "org freedesktop DBus Error NoReply "

After this all systray apps fail to load, namely hplip-systray, Knetworkmanager, dropbox and so on.

If I quit Amarok and restart, after login, because Amarok is not autostarting, everything works fine...

Any ideas?

not a solution but you can force it to not autostart in systemsettings -> system admin -> startup shutdown -> session management -> applications to be excluded

Ok, thanks, but I would like to debug it a little...

Is any log file where I can see KDE info or information that can be usefull?

System logs, show nothing...

Also this only started to happen when Amarok was upgraded...

you can try using kdebugdialog and selecting only amarok
error messages would be in ~/.xsession-errors

not sure if this will help debug but ............