I have the same mobo/cpu/mem, so I may be able to help. What are your BIOS settings when the machine reboots? Do you have the mem timings and voltage set per the rated specs?
Feel free to re-flash to 1305. Configure your BIOS as follows:
FSB: 266
DRAM: 800
VCORE: AUTO
VDIMM: 2.1
SPD: DISABLED
TIMINGS: 4-4-5-15
(note: the timings order in the BIOS does not match the sticker on the mem)
HYPERPATH 3: AUTO (disable this when you eventually overclock)
Disable whatever components you're not using, like onboard audio, jmicron controller, second ethernet, qfan, etc.
Then, test your RAM with memtest86:
http://www.memtest.org
If you get any errors, run the test with each stick separately. If you get errors on only one of your sticks, it's a good bet that that stick is bad. Same thing happened to me with my first pair. If you get errors on both, that's a tougher call. If you get no errors, boot into windows and run stress test with Orthos Stress Prime (blended).
http://sp2004.fre3.com/beta/beta2.htm
Update: It just occurred to me that I saw something recently about problems with the X-Fi and certain chipsets. I don't remember anything else, but you may want to add to the above a test of your rig with the X-Fi disabled.
-phil