Random Freezing

Hi everyone this is my 1st post but I've been visiting for quite a while.
About a month ago I built myself a new system and have been plagued by random freezing.
First of all I couldn't install Vista 64, only way I could install was to disable all USB functions from the BIOS.
Once installed system randomly freezes with the HDD light on and requires reboot, can happen anytime.
Discovered that disabling all USB functions in BIOS again stopped the lockups.
This happens in both Vista 64 sp1 64bit and XP sp3 32bit.
Weird thing is it doesn't do it when I swap out for an IDE HDD.

Have tried two brand new completely different Sata2 HDD drives, different cables, two different copies Vista 64 and XP, two different sticks RAM both cleared Memtest86+, swapped Sata DVD/RW to IDE and back, all kinds of physical drive arrangements, all BIOS updates available, all hardware drivers available, all OS updates!

I'm out of ideas, help would be greatly appreciated.

System Info:
X3 720 2.8Ghz - stock cooling
Gigabyte GA MA78G-DS3H Rev 2.0
Hi-Power 800w PSU
2x 2Gb OCZ Titanium 800mhz 5-5-5-15 2.2v
Optiarc DVD/RW SATA
Seagate Barracuda 7200.11 500gb SATA2 (not affected by firmware issue)
Maxtor Diamondmax 320gb SATA2

I meant that the Seagate 7200.11 500gb and 1Tb had firmware problems with some of their drives but that the one I have is unaffected.

Thanks for the reply.

I checked with Seagate, the firmware version for my drive is SD1A which was not one of those affected.
I have also tried a different SATA2 HDD with same result.