It's not a bug but behavior change. VFP8 can detect table corruption which previous versions wouldn't. See INFO: Data Reliability Enhancements in Visual FoxPro 8.0 mskb #814131, SET TABLEVALIDATE Command help and SP1 Readme for details.

>Is there a bug in VFP8.0 (same behaviour with SP1)?
>
>You can recreate the problem by running 2 instances of VFP8:
>
>workstation #1:
>USE \\server\sharename\file.dbf shared
>? flock()
>
>workstation #2:
>USE \\server\sharename\file.dbf shared
>* generates a "file is in use by another" error
>
>However, even with the table locked by workstation #1, I can open it using good ol' Foxpro/DOS 2.6 on another workstation.
>
>We noticed this issue in our Westwind Web Connection app. About once every couple of days our app can't open a file and generates an error message. Presumably this is happening right at the exact moment when a file is locked by another user (presumably they are appending a record, or doing some other operation that locks the file for a second or two).
>
>We could fix this by changing our SET REPROCESS behaviour, but that might have big consequences that could mess up other parts of our WWC app.
>
>This seems like a bug in VFP8 and VFP8/SP1. Is it?
>
>.. Geoff Bannoff
> Vancouver, Canada