iMac - Slot Load G3 USB ports.

my brother has an iMac 600Mhz Snow CD-R, appearently his USB ports dont work anymore. at first he thought his computer was freezing because he would move around the mouse and nothing would happen. he plugged the keyboard and mouse into a PC he had laying around and they worked. anyone know if this is a common problem? where can he get one if this is really his problem? and is it soldered to the logic board?

thanks