Corsair Dram- Gigabyte GA-EX58-UD3R MOBO

[ecca]

Hi all,
I've built my set-up as per my spec in my profile.
Intel core i7, Gigabyte GA-EX58-UD3R motherboard.
I'm having memory problems.
I bought 8 gig of DDR3 PC1333 but the computer gives various beeps and won't start at all with any combination other than one, 2 gig module in.
It only runs with 2 gig of RAM .
Thinking it must be cheap DDR3 ( it was, £80 the lot ) I bought a Corsair XMS3 6 gig matched kit " recommended for Intel Core i7 Processors "
Part No.TR3X6G1333C9
The computer fans start up for a bit then switch off and then back on ad infinitum, not even a beep.
It does the same with any configuration of the 3 modules, or any one on its own.
So I'm back to one of the original cheap 2 gig DDR3 module.
What am I doing wrong ?
HELP !
Cheers
Eric Thacker