This was caused by buggy and misconfigured bios, I cannot reproduce it anymore and system runs stable with same kernel.
** Changed in: linux-source-2.6.20 (Ubuntu) Status: Unconfirmed => Rejected -- BUG: unable to handle kernel paging request at virtual address feda6658 https://launchpad.net/bugs/82873 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs