I have moved away from LXDE and used XFCE instead, seems more stable and no issue with the black screen as you mentioned. I once tried to pxe boot Windows XP and it was horribly slow. Took over 5 minutes to boot, just not good enough. I wish it would work as the view client on windows seems the most stable but i just don't want to manage the OS on each client. For now though, Ubuntu with XFCE does the job. I have over 100 clients pxe booting with Vmware view, it sure makes our lives easier.
In regards to USB, it shouldn't matter what vendor hardware you're using, it should work regardless.