Default usb connection win 8

Hello everybody, I got a problem with a p500 who's not recognized from win 8. When I connect with usb cable, OS made the classic sound but after pressing usb mass storage on phone no folder appear on pc. this O1 equiped with 2.3.7 (CM 7.2). with or w/o debug mode is the same.
I tried with a different p500 with 4.0.4 (JB revolution) and all works perfectly, also as access point. How can I exclude usb hardware problem on first device? could an upgrade to 4.0.4 solve my problem? best regards.