UPDATE:
Seem to have solved the problem. Here's what I did:
Reboot, Hold Shift Key pressed --> this booted the system in Safe Mode
Logged in, then gone to System/Library/Extensions and deleted VoodooHDA.kext
Rebuilt cache (in terminal, run "sudo touch /System/Library/Extensions"
Repaired permissions (open disk utility, select ML partition and press Repair disk permissions button
Reboot
And YAY, it works.
Now, of course, I don't have the soundboard installed anymore, but don't mind 'cause I was using an USB one anyways.
NOTE: All of the above are not my merit; it's info I found here on the forum, posted by other users. Don't exactly know what the last 2 steps do, or if they are always necessary, but in my case it worked.