Posting problems

[caligulaofrome]

I've had this machine for about half a year and it's been overclocked as long as I've had it. It >48h dual prime95 stable, passed memtest, etc and about a month ago, I encountered the first problem when I restarted my computer. It stopped posting (the little light on my monitor stayed orange when it's supposed to turn green). I turned off my psu, unplugged it, cleared cmos, etc and it posted and booted the way it always does. I didn't give it much thought andhad to repeat those steps a few times (it would post successfully every time I did it), but a few days ago, it would only post after repeating that procedure multiple times (I thought I was lucky when it'd actually post). Yesterday, I somehow managed to get it to post with 2x512 running in dual channel mode, so I ran memtest and clicked ESC after passing it about 10 times, thinking it was probably OK. After clicking ESC, it stopped posting again. The sticks of memory pass memtest >20 times without a problem when I test them individually in the top yellow memory slot, but my machine refuses to post all the time now when I have them in dual channel mode or when they're both in there at the same time. When I'm lucky enough to get into Windows, Prime95 doesn't detect any errors. Any idea what's wrong?

 

Oh, and running everything at stock doesn't help matters...