Thermatake spedo advance : one front USB not working

Hello.

I have just built my first home-made PC and, much to my surprise, almost everything works perfectly on the first try. Yoohoo. Probably partly thanks to the good people here who gave me good advices on the components I should buy.

I only have one small problem.

On the front panel, there are two USB ports. One of them is working alright but the other one is not.

Relevant elements from my sysem :
case Thermaltake Spedo advance
MB : ASRock X58 Extreme
Powersupply : Corsair TX 850W
(I hope that's enough information)

Inside the case, there was one (at least I only saw one) plug labeled USB to plug on my Motherboard. I thought I was good with that, because the motherboard documentation said that each of the MB's USB plug was good for 2 USB ports.

However, as I said, only one port is recognizing whatever USB device i plug into it.

Do you think I made a mistake ? or is the port simply defective ?

Thanks for your help.

Sykurmoli