So it seems I have one unhappy customer up until this day, Here's what happened:

1. Sold him a Motherboard + CPU combo on May 16th.
2. Shipped the next day & arrived 3 days later.
3. Two weeks later he sent me a message telling me the board doesn't work with BAMT(a pre-built BTC mining software) & calling me a liar because he can't get 4 GPUs to work with the Mobo on linux.
4. Now he's hinting about "making a big deal on the forums" & demanding for a full refund shipping included.

Now I'm not very familiar with linux mining, but I've been happily mining with the board on windows with multi-GPU since last year. I've built many multi GPU rigs and I do have a few theories of what went wrong with his setup, unfortunetely he refuses to work with me. Weather this board is just incompatible with Linux(highly unlikely), or maybe his just incompetent at building rigs.

Part of me just want to refund him and get it over with, it's a small transaction after all. At the same time, I don't appreciate being called a liar and threatened to "a big deal on the forums". So far, everyone I've dealt with on the forums are happy with what they received, so I'll keep it open and post what happened to see everyone's opinion before making a decision.