eMach T3065 'freezes' NO kybd/mouse so no BIOS

Hi All,
I have an eMachine T3065 that started freezing up on me when I removed
& replaced THE SAME power supply (NO other changes). At first, it would
run fine, then freeze. Now it just freezes at the login screen - NO
keyboard or mouse. Apparently BIOS is not recognizing keyboard either
because it doesn't respond to DEL, F1 or F2. The power supply has
always been connected to a UPS since purchasing new in 2004. Pwr
supply may be coincidence but nothing else was changed.

Any ideas?? - Thanks

Jack