UNOFFICIAL BIOSTAR TPower I45 M/B

[mattkosem]

i found this in the newegg specs for a single 4870...so...it might behoove you to at least borrow another PSU to see if the PSU could be the problem:

That requirement doesn't look completely correct. 4870 definitely has two connectors. See pics:
http://www.nordichardware.com/news,7798.html

--Matt