As the others have mentioned, there are some problems with vfp3 and large amounts of memory.
Use the /maxmem switch in the OS-boot.ini for temporary fix, but get your client to buy a newer version of vfp. If your client is nearly broke, let them search on ebay for a vfp6 or vs6 version, which is very stable after SP3 (better take SP5) even if missing some very nice new features, or move them straight up to vfp9 starting with the beta right now, if they usually have to pay for their own programmers time.

my 0.02 EUR

thomas