I had a problem with my G25, where it would work but the usb headset wouldnt and visa versa. The solution was to intoduce a powered hub for one of the other, the problem was too much voltage being sucked off the MB for all usb devices to work properly. The other issue I struck later was randomly it selected any number of buttons at once. Made it impossible to drive in a race. Logitech replaced the wheel but it still persisted, although to a lesser degree.
the closest I could narrow it down to was the fact that I had a number of mods in rF and something was upsetting the gp79 install.
I installed rF lite and only used one mod per instal and all seemed fine.
On my new computer however it "sometimes" skips a gear in sequential mode. Setting it back to gated selection and then back to sequential seems to fix it, which might indicate a problem in the selector, who knows....
Either way, frex is looking good.... if they ever get drivers for Vista, which seems unlikely due to the lassuit with Immersion, my latest indicators from the techs there say that drivers for windows 7 may happen first....