S5 100U digital input

One of my S5 100U PLCs(103 CPU) shows lit red leds on all digital input cards.At times the problem clears after several resets.On Monday I lost the whole program after a power cut.After reloading the program,the same problem is still there.The power supply is currently giving an output of 20VDC can this be the root cause.
Please assist.

chakanyuka,

You should think about replacing it with a S7, it may just be getting old...