very odd thing with my OC AMD

Hey, im new to this forum (but not to OC) so hey every1
i looked up a lot of forums and didnt find any answer to my problem, so thanks if your reading this...

I have a really weird problem... my brother just bought a new cheap computer (not for gaming) which has:
AMD Athlon 64X2 3800+
Abit KN9 SLI Socket AM2 mobo
4X 1Gb ram @ 667 Mhz

he brought it over so ill OC the cpu.
i started really slow and didn't want to take any chances with the ram so i kept it under 667 the whole time...
i got to 2.3Ghz for the cpu and 660 for the ram, and then I started testing it.
it passed a whole night of testing and everything looked great. i even installed some games (it has 7900GT Gigabyte) and it ran perfectly.
after a while i turned the cpu off, and the next day when i try to turn it on i get NOTHING !
the computer wont boot...
so i reset the cmos and it boots fine... i OC it all back, and this time i stopped at 2.25. tested it and everything is cool. i left it for a whole 24 hours just to be sure its stable (max temps were ~55 Celsius). then i turned off the computer and when i turn it back on it wont boot.
(even if i dont turn it off but go to sleep mode it wont boot back up)... so i again reset cmos

it seems that as long as it was on before it got OC it will OC to some good results (i stopped at 2.3 Ghz not cuz it crashed or anything... so im pretty sure i can squeez more out of it) but if i turn it off or go to sleep mode i need to reset cmos...

any1 got any suggestions
thanks ALOT
BTW - sorry for any spelling mistakes (English aint my mother language)

First thing I would do is update the bios if possible, and it seems warranted.

Welcome to the forums.

Isn't it enough to reset the PC when it won't start ? I had such experience with low end Asus board.

Could be the power supply isn't strong enough to kick it on at that speed, but if you boot it at stock speed and then oc without shutting it off it's fine.

Could also be that even though it seems stable for 24 hours, it's really not completely stable. Maybe try repeating the 24 hour test you did at 2.2 ghz and see if you have the same cold boot issues. It's more than likely a limitation of the board if it's not a weak power supply.

Thanks !

Hey every1. first of all thanks for your fast an reliable comments...
so far it seems that flashing a new bios did the job (!) i turned the cpu off waited couple of minutes turned on and everything is going smoothly (and even on lower cpu voltages...)