I'm using Gentoo with KDE 4.4.3. Plasma crashes everytime when I close my laptop.

Just close - wait for a few seconds - open - no plasma
How do I fix this?)

If it might help - laptop is ASUS X51L

Have you tried using the KDE Crash reporter to generate a backtrace? ( Developer information tab )

I rebuilt plasma-workspace and plasma-runtime with USE="debug", but KDE Crash Dialog doesn't appear after crash. I just see a black screen with open windows.

output in ~/.xsession-errors while I close-open:
http://pastebin.com/nLA00MXZ

any other interesting logs (in /var/log/: everything.log, user.log, kdm.log, errors.log and so on) I haven't found.

And: it happens only when KMS enabled.
What else can I do?

Given that this only happens when KMS is enabled, I am inclined to think it may be graphics driver related. Does this occur if you disable compositing?

bcooksley wrote:Given that this only happens when KMS is enabled, I am inclined to think it may be graphics driver related.

maybe.. but I tried drivers 2.9.1, 2.10.0 and latest 2.11.0 - the same problem.

bcooksley wrote:Does this occur if you disable compositing?

Yes, without compositing it occurs too..

I updated the kernel to 2.6.34 (sys-kernel/vanilla-sources-2.6.34) and plasma doesn't crashes anymore with KMS! So you was right, this was graphics driver or kms related