How do I fix my issue with Sound Preferences in Snow Leopard?

I recently updated my 2009 Macbook Pro to Snow Leopard, and upon doing so, I started having a problem with my Sound Preferences. I need to always use my external speakers, however, whenever I select them as audio output in the Audio MIDI setup, and in the preferences themselves, it ALWAYS changes back to internal speakers seconds later. I can't get it to stick! I've deleted the plist files, reset the PRAM, the SNC, everything! Will upgrading to Lion help this? Or am I stuck?

Really don't want to have to go back to Leopard.

http://youtu.be/zpEV9q2sX5U