Rich,

this may be a bug I encountered in vfp6 and discussed with Alekzey T. from MS quit a bit.

In older versions of vfp sometimes a race condition existed if an alias was closed and another table with the same alias is opened in the next lines. The table you want to open IS open, but with a weird vfp-forbidden alias - as can be verified stepping though all work areas and getting the alias() and dbf().

This is definately fixed in vfp9 and needs a bit of wrapping code in your functions or methods for opening and closing tables otherwise - but verify first it really IS that sucker.

Otherwise you could get a better grip on what the problem is with special logging or vars showing where the error occurs. Another insight by Aleksey was, the error won't happen if a variable with the same name as the alias is in scope - something you can probably only figure out reading the vfp-source...

HTH

thomas