Hi,
Do you have transaction tracking on the table.? I have chasing this one for a while. I have identified what causes it, but haven't figured out a fix as yet, other than disable caching.

What happens is as follows:

Begin Transaction issued
User appends record
User gets half way thru input, then leaves for 20 Minutes
User comes back quits input i.e. Rollback issued.
This causes attempted cache flush, cache too far out of sync with disk, rollback unable to complete correctly.
Get error saying index corrupted.

P.S. Only happens if a lot of Multiuser activity.