I got the same problem with my Gopro HD cam, it charges fine, but can't get into USB mode, and I got another problem, when ever I have charged the cam, I HAVE to pull out the battery and insert it again, else the cam won't turn on, is that normal ?
And the SD card is brand new, and I have had it in a SD-card reader, and it works great.
So if anyone have a fix to my problems I would be happy