Yes there seems to be something in the air with the oem 700 athlon processors. But first I would look At the boards you are using. All have documented problems with processors over 650. The first thing I would do is update your bios, and get the lates Miniport drivers for the VIA Appollo chipset. Preferbably the 4-1 minport driver update. This will update and recognize the CPU to AGP controller, CPU to PCI Bridge and so on. I have been having problems with my 750 on a Epox 7KXA. I did all the above mentioned, and it helped out considerably. I also have 650 on an Abit KA7, This machine runs like dream, not one ounce of fuss.
Good Luck!