I am now pretty certain this has to do with the kernel as the comments in the below bug report reflect exactly my epxeriences after a fresh install of Jaunty 64-bit:
jaunty kernel 2.6.28-11 kernel update renders the system un-usable https://bugs.launchpad.net/ubuntu/+source/linux/+bug/346691 -- [Jaunty beta] many ext4-fs errors https://bugs.launchpad.net/bugs/350268 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs