>I have never had this problem before, however I had for a day commented out the command "Close Tables All." Could this have locked one of the tables open when someone accessed it?

I'd say only if your code doesn't close individual tables explicitly. And given the impact of removing your CLOSE TABLES ALL I'd say the posibility is strong.

By the way, a close tables all would close the quietly VFP-opened filtered results set table too.

good luck