About the only thing I can think of to try is opening the case and making sure the cable from the USB port to the motherboard is installed properly. The ports in the back are probably soldered to the motherboard so you probably have little to check there.
If you have a solution that works, it might not be worth the trouble, though. But if you want to get your scanner working properly, etc., it might be worth putting a PCI card in the PC in question.
Yep, that's what John thought about doing in the long run, a PCI card. He did that USB cable check you mentioned before, by opening the case when the scanner first had trouble. The scanner does work, btw just not using the buttons. You have to activate it manually, but it does fine when I do that.
At least I can easily get the photos off the camera for now, which is what matters most. :)
Brenda