It might be a stupid question and you've probably checked but are you sure the front USBs are working?
Have you tried something else on them?
Did the camera work before?
One of my friends has a similar sort of problem. I went round to his house last week with my pen drive and the front USB just wouldn't recognise it, in fact it locked up the PC. I plugged it in a rear one and it worked perfectly. He plugged in a USB games controller to the front and it worked perfectly. I'm not sure why this would be and the conclusions I have reached are either the pen drive needs more power than the USB ports on the front can give, which is possible I suppose but I consider unlikely or the front USB are 1.1 not USB 2.0 ports and that might be causing some problems.
In short I don't know whats causing it.
If you can't find another solution then my only suggestion is to buy a card reader and connect that permanantly to one of the rear ports. Something like this click here=