This is the follow-up I promised.

Even after all of the changes that I've mentioned, and the checks suggested by others, I was still intermittantly getting my original error on some machines. I decided to look at this error more closely. It occurs in the TxtBtns set of button controls that comes with the VFP Wizbtns.vcx library. It was occurring in the SetAllProp method. This method can be called either with an argument, i.e. a reference to some object, or with no argument. If it is called with no argument,the routine uses THISFORM.

Some time ago, I did an override of SetAllProp in my implementation. My override was basically a shell that enabled me to set a breakpoint. Here is the override I used:

LPARAMETER oContainer
IF PARAMETERS() = 0
DODEFAULT()
ELSE
DODEFAULT(oContainer)
ENDIF

A stack trace when the error occurs shows that SetAllProp() is being called without an argument.
To solve my problem, I just elimated my override code.

I have now tested this without error on two machines that formerly showed the error. Furthermore, Norton AntiVirus and Windows Automatic Update are also running on these machines.

Does anyone know why this solved my problem? I don't see how this code was a problem in the first place. And, if it was, then why didn't it fail all of the time, and why didn't it fail on all computers?

Thanks again,
Jim