Whew!. What it turned out to be was a corrupt class in my main class library. I only discovered this after trying to open every single class in the VCX. Finally one choked with a problem. Interestingly when I compiled the class library just prior to discovering this, it compiled without errors... hmmm...

>Have you tried deleting foxuser.dbf and .fpt and start over with a fresh foxuser? I know when I have a problem with the class browser, I zap the browser.dbf table in the Home() folder.
>
>>I am getting the following error today. It started just before noon.
>>
>>VFP6.EXE - Application Error
>>The instruction at ox77f1d493 referenced at "0x00000000". The memory could not be "written". Click on OK to terminate the application. Click on Cancel to debug the application.
>>
>>The error happens when I try to open a few forms in one project. Pressing OK or CANCEL cause VFP to shut down.
>>
>>Things I have tried to solve the problem.
>>1) I have uninstalled and reinstalled VFP6 (with SP3).
>>2) Got the entire project with files off of backup tape, but they have the same problem.
>>3) Recompiled the class library that the forms are based on. Note not all forms in the project exhibit this error. Forms based on the same class library, but in other probjects do not exhibit this error.
>>4) Deleted PJT and PJX files and rebuilt project. No dice.
>>
>>Any ideas? I will lose almost an entire app if I can't solve this.