Hi Jim. I've been experiencing the same problem beginning October 2010 when I started using a new Windows 7 64-Bit PC. In my experience, the problem tends to occur when I open a SCX file and make one or two quick changes and then try to save the form. If I have the form open for several minutes I do not have any issues. VCX's have never been a problem.

My co-worker Paul has the same hardware - no issues. He is also running the same anti-virus - ESET NOD32.

A while back I did a little a research and SCT files can also be Windows Script Component files. Based on this I wondered if the anti-virus was being a little aggressive with these file and I tried excluding them from the virus scan process. That did not fix the problem. I also ran the Sysinternals FileMon utility and was able to witness where VFP deleted the .SCT file, and then attempted to rename a .TMP to .SCT. The rename failed because the SCT delete wasn't finished. Because the rename fails, VFP throws the SCT file is missing or invalid error.

I don't know if you have figured this out yet, but if you manually rename the .TMP file to .SCT, you can "save" your work. VFP will probably still crashes with C5 error, but the form still works.