Vista - Front Left speaker not working correctly in 5.1 speaker configuration

I have had a 5.1 speaker arrangement on my Vista x64 PC for some time. Today, the front left speaker decided to stop working correctly. When trying to plug my headphones in to a rear jack on my motherboard (onboard sound), I noticed that sound was only coming through the right earphone. I decided to give up with trying to listen through my headphones for the time being and plugged my speakers back in, only to find that now my front left speaker wasn't working correctly. I tried to adjust the balance on my speakers, as I thought I could hear a whisper of a sound through the front left.

• The front left speaker is producing sound, but at a greatly reduced volume to the rest of the speakers, I have to set the balance to the following to make FL and FR speakers 'the same' volume (by ear).

FL volume: 100
FR volume: 0

• I have my speakers plugged in to 3 jacks on my motherboard (out of 6).
  • The green jack for FL and FR.
  • The black jack for RL and RR.
  • The orange jack for C and SubW.
• I have been unsucessful installing Realtek (which is a shame, because on my last motherboard I was able to solve the problem with that somehow, but I can't remember how) as it states the drivers are not supported. Which I'm assuming means my motherboard doesn't support it.
  • My motherboard is an MSI Intel p35 Neo.
    • I have had this setup working fine for around a month.
  • My speakers are labtec (but I don't see how that would matter).
• I am currently using the normal drivers that come with Vista.

Any ideas?

Regards, Graham.