This is more of a curiosity question than a troubleshooting one, but I'd like to see if there's an answer anyway.

The other day I woke up to find a BSOD with an "Error IRQL not less than or equal" prominently displayed on top. Wouldn't even boot to safe mode, just kept giving me the same error. Did some quick research, and found out that it's usually a driver issue or bad memory. Since I haven't installed a driver in about a month and haven't had any trouble, I grabbed Memtest and tossed it in. Sure enough, within 5 minutes, there was an error or three. I let it run for 5 hours, then came to the realization that I should be running it one stick of RAM at a time. Duh. So, I popped out one stick, ran memtest overnight, no errors. Switched sticks, ran for another 8 hours, no errors. Booted to bios, checked settings (all normal for mobo/ram) and decided to just see if it would boot to windows. Sure enough, it did.

So, I went to lunch, and came back to see the same error message. Wash, rinse and repeat the same process. I called Crucial and they're sending me new RAM, so I'm not too worried about that, but I was just curious was to why it would error out, throw a couple errors, then go back to normal.

Edit: I should probably mention this: P5K Deluxe Motherboard, 2 gigs Ballistix 800mhz, and all the drivers for the videocard and whatnot are up to date.