Had the same problem, related to usplash I think because removing it solved it. Since the latest usplash update (0.4-25), everything's fine.
AMD64 x2 3800+ -- BUG: soft lockup detected on CPU#0! https://launchpad.net/bugs/60053 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
