That's a definite possibility; could also be the disk going bad.
Of course a power spike/drop could have the same effect... having a UPS isn't always about keeping the system up, a good one also 'cleans' the incoming power.
After every x mounts, a disk will be fsck'ed anyway.
This situation calls for an 'offline' fsck by the sounds of it. In fact, if its the root disk, you can't do it online for obvious reasons