[Magnus]

I Googled the panic message (assume you did as well) and found this which has the following suggestions:

You should try the standard troubleshooting suggestions:
Apple - Support - Mac 101 (see the "My Mac needs help" section)
macosxhints.com - Twenty steps to help diagnose and fix system issues
OSXFAQ :: View topic - General Steps in OS X Troubleshooting
The X Lab: The X-FAQs

In particular, be sure to do "Repair Disk" (different from "Repair Disk Permissions"!) in Disk Utility when booted from the Install CD/DVD. I.e. you restart from the Install CD/DVD, then run the version of Disk Utility that is available from one of the menus there.
See this Apple doc:
Resolve startup issues and perform disk maintenance with Disk Utility and fsck

Be sure to disconnect all non-Apple peripherals.

And check the RAM with 'memtest':
Memtest OS X - Home

Some of it we've suggested, but not all of it. Tell us what you have tried so we know better what to suggest.