Installed 11.04 x64 on my Dell E6500 some time ago and it freezes sometimes when I close my laptop.
After some search I did following actions:
disabled Sync to VBlank in Compiz settings switched off screen saver
But is still freezes. Last one happened few hours ago: I was able to move mouse, but that's it - I couldn't click anything.
I pressed CTRL-ALT-BACKSPACE and restarted X.
uname -a: Linux rgwork 2.6.38-11-generic #48-Ubuntu SMP Fri Jul 29 19:02:55 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux
dpkg -l on pastebin
Update: it just froze again. I can move my mouse, and I see that the cursor changes to when I move my mouse (probably when it's going over some textfield), but screen remains blank.
i tried to go to sleep mode and wake it back, but screen remained black.