>Neil and All,
>
>I have found the problem - I was using ESET Smart Security AV and personal firewall but recently changed to using the free Comodo AV and personal firewall - then the problem began but intermittently so there was no immediate connection in my mind. I have now uninstalled Comodo and gone back to ESET and the problem has disappeared.
>
>I suspect that the rapid creation and deletion of the ERR file during VFP project compilation causes a problem for Comodo AV (and possibly other AV products) and this is the problem. Even when I told Comodo to ignore the drive where the project was being compiled it still had the problem. Only uninstalling Comodo resolved the issue.
>
>Thanks

Thank you Jos,
I'll keep that in mind.