When you have an instance of the corruption, post the output from CHECKDB please so we can see what the corruption is. Could be a number of different things - my guess is that invalid data is being entered into the database (which is possible in 2000, but not in 2005 onwards).

When you get the corruption, do the following:

DBCC TRACEON (2570)

GO

DBCC CHECKTABLE (tablewithbrokenindex) WITH ALL_ERRORMSGS, NO_INFOMSGS

GO

DBCC TRACEOFF (2570)

GO

And post the results.

The traceflag enables some undocumented column data type checks that I put in to 2000.

Thanks