eMac w/PS2 Keyboard/Mouse

Greetings folks,

I have a PS2 keyboard/mouse combo that was once connected via a PS2-USB adapter to a Mac Mini in a setup that was not perfect at all times but seemed to get the job done.

I decided to switch this out for the Mac keyboard I had with the eMac that does not get used nearly as often -- oddly enough, the setup does not work in the eMac: the mouse does not move and the keyboard does not respond.

Both systems are running the most up-to-date versions of OS X Tiger available as of this posting; the eMac is the last model Apple made, with a 1.xx GHz PowerPC processor, and the Mac Mini is the 1.42GHz Core Duo model.

Any suggestions on how to troubleshoot this? The keyboard and mouse are really cheap so I wouldn't be too hurt if I had to ditch them, but I figure I'd ask the experts before I put it out to pasture. So, experts?