So i'm really not sure if this should be posted in the mobo forum or the cases forum so i apologize if its in the wrong one. Anyway here's the deal.
I have a brand new Asus Rampage IV extreme Mobo and a Thermaltake Level 10 GT case. For some reason if i have the top USB 3.0 ports on the case plugged into either of the two Mobo USB 3.0 external connectors the system will not get any power (no fans will even spin up when trying to power on, the power supply doesn't even spin up or have the LED light up.) But once i disconnect the external USB 3.0 cable the system boots fine with no issues.
Does anyone have any idea why this is happening? Is the mobo faulty, or something wrong with the case cables that's preventing the system to allow itself to start?
Assuming you can replicate this reliably, this is awfully weird, and it sounds like you've just got a bad mobo. There's nothing plugged into the case's front USB 3s, is there?
I think either you're somehow knocking something out of whack when you plug in the cables, or you've just got a bad mobo and you'll have to RMA. Try to replicate the issue plugging in the cables very gently and carefully, and then RMA.