[Solved] Memory problem?

Ok just wondering if someone can check my conclusion that a RAM module is defective.

New build PC using Gigabyte GA-M790FXT-UDP5 Rev 1.0, AMD Phenom II X4 955 Black Edition 3.2GHz, Corsair XMS3 4Gb twinned pair, ATI HD 4350 (stopgap card) and a corsair HX 620W PSU plus seagate HDD and HP DVD drive.

Computer would not POST. Lack of speaker made that difficult to work out. Removed both modules and the machine POSTed with error. One module back in. Machines POSTs and boots. Ran memtest (via Ultimate Boot CD) on module. Passed that battery of tests. Tried RAM module in all slots, all POSTed and booted fine. Removed working RAM and installed the second module on its own - nothing. Will occasionally turn the monitor on but then hang, not displaying POST screen or responding to any input from keyboard. Removed RAM and flashed BIOS to latest F5 version to see if that would help but no joy.

Am thinking I have a defective RAM stick but just wanted to check that I haven't missed something obvious before I go to scan.co.uk for an RMA.

Cheers

Tim

If Stick A will allow boot, alone, in any of four slots, and Stick B will not ==> Stick B is not the same as Stick A lol.

RMA the pair.