Your not alone.I have a Trust wireless (infrared) keyboard and mouse.The infrared sensor,connects to the PS2 keyboard,and mouse "holes",at the back of my PC.The sensor has direct line of sight to my keyboard,and mouse.Many times the keyboard mistakes letters,or misses them altogether.Sometimes the mouse will "do it's own thing",even though I've adjusted the settings in Windows.I too have changed the batteries,to more "upmarket ones"

but still I have trouble.As both were a combined xmas present,I can't really bin them,but I have been tempted.Apparently,it is common with (infrared) keyboards,to "go awol".I have been told to invest in a Bluetooth keyboard,and mouse.Out my price range at present,but I keep hinting to family members for next xmas.