[CentOS] Root fs suddenly goes r/o

Out of the blue, dmesg on my HP Proliant w/ a SCSI disk gives loads of messages like this one:

EXT3-fs error (device dm-0) in start_transaction: Journal has aborted

Then the root fs goes read-only, so little else can be done on the machine. LVM locks up. At restart, fs needs a reboot to recover after fsck. The host starts up ok, then I am given some more minutes before the problem reappears. This is stock CentOS 4.4, never have gotten to update it because of this very same problem.

System logs say SCSI I/O error, but SMART says no problem has been found, neither does badblocks (run from a rescue CD bootup). SCSI cabling, terminator, etc has been checked.

What should I investigate next? Is the disk condemned? TIA