Actually, I figured it out, it was kind of odd.

The Abit KG-7 RAID mainboard supports ECC memory, which I was using. One of the memory modules was failing, but the ECC was keeping it working reliably...turn off ECC, and everything goes wonky.

When I went to my ASUS A7V8X mainboard, being a KT400 chipset instead of AMD's 760, it didn't support ECC RAM, and so it ran my DDR modules, but with ECC off. Instant problems. I called Crucial and got the offending module replaced, and everything is now fine. Was truly a pain in the rear to figure out though.

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AMD Athlon XP 2000+ aircooled
ASUS A7V8X-RAID mobo, Enet, SATA, 1394, USB2.0, all dat junk
512MB Crucial DDR
AOpen HX-08 case, Enermax 430wPS
80GB WD Spedial Edition 8MB cache
(all SCSI) Plextor 40x CD, Yamaha 8x4x24 CDRW, Seagate DDS2 DAT
Visiontek Geforce3 Ti200
Adaptec 2930U2 SCSI
ATI TV Wonder
SB Audigy MP3+