It's not the soundcard. (And you haven't killed it with phantom power.) It may be your motherboard. I had the same problem when I built my new PC last spring. I could only use one audio app at a time and had to reboot to switch. Sometimes I got the heavily distorted audio, too. I reinstalled Windows several times with no change. I exchanged motherboards, but it wasn't until I upgraded the MB that the problem was fixed. Fortunately, everything was under warranty.
Anyway, that's my experience. I have no explanation for it's being okay and suddenly not working. In any case I would check to be sure I have the latest drivers for my soundcard.
Windows 7 Ultimate x64, Reason 7, BIAB 2013
Intel i5 2500K 3.3 Ghz, Gigabyte ZX77X-UD3H, 16 Gb Corsair DDR3 RAM
OCZ 60 Gb SSD, WD 1 Tb Caviar Black 7,200 RPM HD
Zotac/Nvidia GeForce GTX 560 2 Gb, NZXT H2 "Silent" case w/liquid cooling
Presonus AudioBox USB, Behringer B2031A, JBL PSW D110 sub
Kennesaw (Atlanta), Georgia, USA