Malcom,
Maybe this will work for you....
get rid of the filter, then when running in DOS
do a select to a temp table...if need be create the index with the filter on the temporary table...close the real table and set the alias() of the temp table to the name of the real table.

Of course you'll need to merge new and changed records and remove deleted records....but it should work.

Maybe someone has a better idea???

Rick
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>Situation: I have a 1GB data file accessed by both FoxPro 2.6 DOS and VFP 6 applications on Windows NT. The file has a filtered index - not my idea - I just support it! :-)
>
>We get index corruption causing exception errors every time both apps use the data. Remove the filtered tag and its fine. Use just VFP or just DOS, its fine. Recreate the tag and let the users loose on it both applications- it falls over again. Trouble is, the DOS application requires the filtered tag - we have to have it in. Any ideas?
>
>You can tell the index is trashed by browsing after GO TOP or LOCATE (there are records above the 'top' record and the cursor selects multiple duplicate records). Also scatter followed by a gather on particular records causes VFP to bomb out completely (the NT message is to do with 'access denied').