The AWUS036NH does not work out-of-the-box with virtual installation of BackTrack 5. I tried in both VirtualBox (VB) and VMWare (VMW) and problem persists. You can browse the web, but you cannot use aircrack-ng. (FYI, I have been using BT4 installed into VB with no problems and am familiar with using virtualization).
Anyway, to test my suspicion, I installed BT5 in USB drive and the AWUS036NH works perfectly. I can enable mon0 with no problem. I can inject. I can do everything.