microsoft comfort wireless keyboard problems

Please help,
have installed wireless desktop set, ps2 connection only for keyboard and usb/ps2 connection for mouse. Mouse works fine with either connection, the keyboard is a nightmare.
Works fine on one PC reboots fine and no issues. The other PC doesn't get past POST. Blank screen and no beeps after POST or messages. Both PCs run on XP Professional.
Have even done a total clean install to get rid of any software or device conflicts, only has monitor, keyboard and mouse attached. Works fine with old cabled keyboard and mouse.

PS. works if I boot with old keyboard/mouse and then change over to wireless whilst running but when reboots same old problem

Please please help