<snip>
>>>>Update: It occurs with VFP8 projects as well so its not project specific or VFP 8 or 9 per se. It seems to be related to the creation and over-writing of the ERR file during the compile process. Not sure what though.
>>>
>>>It sounds to me like rights issue. Are you running as administrator? Is UAC on?
>>
>>UAC is on (as it has always been before). My account has admin rights but is not the administrator account.
>>
>>It is a local partition drive.
>
>Did you have the same error if you right click on VFP icon and choose "Run as Administrator"?

Sometimes yes, sometimes no - whether under my account or Run as Admin. Sometimes it compiles properly, sometimes not.

I thought it might be the AV (using Comodo Firewall + AV combo) but if I quit Comodo it still happens. This only started since this afternoon but I cannot think of what has changed in the last few hours.

Should I reinstall VFP 9 perhaps?