1gig Titanium 10.3.9

Reseting power mgr. and zapping pram did not work.

Here's what happened:
I hooked up an external USB/firewire hard drive. It can be powered either through firewire or usb. Like an idiot, I hooked up both firewire and usb connections. Now my USB doesn't work, though firewire seems to work fine. When I hook up my optical mouse to USB, it doesn't light up. Instead, a faint buzzing sound now comes from the circuit board - and goes away when I yank the optical mouse.
Any idea on what the problem can be and how much will parts and labor cost? I am hoping that it's just a matter of replacing something so that I can aviod labor.

Thank you kindly,
Chris