help needed. XP don't recognize my usb anymore

about two months ago, I installed the base suite on my usb mp3 player (GenX 256MB USB 1.1 mp3 player). then I added the applications I wanted to use one by one. at first few days everything was ok altough apps. work a bit slow. but then when I plugged my usb, windows XP didn't recognize it. I think I had plugged it out while some apps. on it were still working. now it is useless. I have tried it in four different machines, (even on a mac!). I reinstalled its drivers from cd (there is no firmware update). nothing worked.
actually it is working; I can open it normally and record voice on it. there are no mp3 songs in it, but if there were any, I think I could be listening to them. but the problem is that it does not connect to the computer. so can not transfer data.
sometimes when I plugged it, in no less than five minutes time, xp sees it as a removable drive but when I try to explore its content or format it from the menu by right clicking, an error occurs that says can not access the device.
is there any way to recover my usb. or is it completely useless now? Actually I know the device is still working so I don't want to throw it out. any help is welcome. thank you.