[ubuntu] 13.04 Random Freeze

hi everybody!
After 13.04 upgrade (or fresh installation) my laptop (DELL studio 1558) freeze after few minutes of normal use. The only solution is to push power button and reboot.
I get the following error message (see the pictures)

thanks a lot for help!

2013-04-27 11.19.18.jpg2013-04-27 11.19.39.jpg

Attached Images

• 2013-04-27 11.19.18.jpg (84.8 KB)
• 2013-04-27 11.19.39.jpg (99.0 KB)