Using source control with Visual FoxPro is, well, a royal pain in the ass. The project integration isn't worth the effort, and Visual SourceSafe sucks anyway. The whole idea of marking files read only to determine if you have them 'checked out' or not is just silly.
A few years ago, I started using CVS to save my VFP repositories, and instead of project integration (which completely blows, see above) I just chose to manage the source control update/commit cycle independently of VFP.
This situation was much better than SourceSafe and project integration, but I quickly noticed some problems that required me to always be manually checking to make sure everything worked correctly:
Enter scX. I took scctext.prg, which is distributed with VFP, and extended it into a project hook that saves vfp binary files into text renditions, and loads text renditions into vfp binary files. This happens pretty much automatically as needed, and allows single text files to be saved to the repository instead of double binary files.
I've released scX to the public under an open source license, and it can be downloaded from Ed Leafe's download page at http://leafe.com/dls/vfp.
scX brings up its own set of problems, but the situation is much better for source control in my opinion. If you are struggling getting source control working correctly with VFP, perhaps you should evaluate scX.
Also note that I've switched from CVS to Subversion which is a much better product, still free. I highly recommend a scX/Subversion system.
I've also made scX available from my Subversion repository, so if you have the Subversion client you can issue the following command to get it:
svn checkout https://svn.paulmcnett.com/Scx/trunk scX
Or, you can just browse the repository online.
scX hasn't been fully tested, and should be considered experimental. I've been using it for my daily use for well over a year now with no corruption, but consider yourself warned anyway.