|Is it one of those combination ps/2 mouse port, IR port and USB mobo connections?|
The fact it shows power doesn't mean it's working or even good. Check in cmos/bios setup and see if there's an option to enable/disable USB.
If everything's enabled but the ports aren't detected then just assume they're bad and buy an add-on card. If you're running 98 SE you can get a USB 2 card, just make sure the necessary drivers are supplied.