Hi, I've been using a system with following configuration for last two years with really good performance.
CPU: AMD Athlon XP 2400+
M.B: MSI VIA KT400
RAM: 384MB PC2700 (128 + 256)
O.S.: Windows XP

Now, I am facing a strange problem for the last few days. Whenever I try to boot my PC after keeping off for 5/6 hours. It simply doesn't boot. The CPU LED is on, fans are turning. But there's no beep & no display in the monitor. Interestingly eache time after I disconnect the RAMs from their slots & connect them again, everything is alright. Att first I thought may be one of my RAM chips or slots may be damaged. But both of my RAM chips & all 3 slots seem to be ok since I can boot in all 6 comibnations. Can anyone give me an idea about what's going on?

Try reseating the motherboard power connector a couple of times. It might not be a RAM problem at all. You might be jiggling the power connector when unplugging/plugging the RAMs.

Do yourself a favor BACKUP!

Report Offensive Follow Up For Removal

You could try cleaning the contacts on your ram, and possibly the contacts in the slots.
See response 3 in this:
http://www.computing.net/hardware/wwwboard/forum/44009.html

You may also be experincing the beginnings of your power supply starting to fail.