Audio Issues - Please Help!

In short, I'm having trouble playing audio from programs. iTunes, Safari, Firefox, quick view, Quicktime player, and VLC give me no audio, although I can hear audio from SOME system sounds (I don't get sound when raising or lowering the volume, but I do when deleting trash, getting alerts, ichat noises.)

This was the situation when I first noticed the problem:

I was recording a minecraft video with a paid version iShowU (standard) and I got a notice that the framerate was going to slow because I was running out of memory. I stopped capturing and continued playing minecraft for a bit (iChat and minecraft audio working). I noticed afterwards that I couldn't play music in itunes and then discovered that I was having audio troubles with a few other things.

I've run a virus scan with ClamX (I ran this because there was something odd that happened a few days ago, but I don't think it's related) that came up with nothing. Checked that all the settings were correct with the Audio MIDI Setup, all applications and programs are up to date. I made more space on my hard drive and removed the videos that I was recording to an external hard drive. Restarted multiple times before and after installing updates.

[EDIT] Realized I'm not getting audio from minecraft or the other part from ichat now.

I'm using a 15" Macbook Pro, OS 10.6.8. If I'm leaving out any important information let me know and I'll edit this post.

Any and all help is extremely extremely appreciated. I'm usually one to figure these things out myself but this time I'm truly stumped.

Audio DOES work in:
SOUNDS for ichat. It will show that it receives my levels, but I can't hear the person on the other end.
System sounds - deleting trash, alert sounds

Audio DOES NOT work in:
Firefox
Safari
Alarm Clock 2
Quicktime
Quick Preview (spacebar on an item)
VLC
iTunes
Minecraft

[EDIT 2]: I have absolutely no clue how, but it seems to be fixed now. I was looking at my installation disks and it said press "D" while booting up to do a hardware test so I did. It said nothing was wrong but upon booting up, my audio now works.

 

Thanks for the advice, will try this in a moment and report back.

 

No luck, still not receiving audio from any of the programs.

Any other ideas?

[EDIT] Also, I'm not receiving audio when using external speakers or headphones either.

I know this shouldn't be possible, but could my recording software have written over important files? I have no idea what could have gone wrong.