Strange thing happened to my S2

I've run countless custom roms on this phone without a problem. I've always been able to reflash back to stock without a problem. Battery life is extremely important to me and i use the stock rom as a basemark. After loading CM7 one day something weird happened when i went to drop back stock the phone would reboot immediately after plugging in my usb cable. Everything else worked fine. Here's the really strange part, when i loaded AOKP it worked fine. Drop back to stock, same thing. I found some other stock images. I loading them and everything is fine except now when i plug in the usb the phone only appears as a media device. Any thoughts?