Help diagnose what is forcing my audio level to zero intermittently

[WizardOfBoz]

This affected both my T61p and my W530. I'll be sitting there, listening to music or a youtube video, and the sound level will decline to zero. Nothing else (no other programs) happening. If I try to increase the sound level, there's a program fighting me - so as long as I keep my finger on the "+" sound key, or on the mixer to increase sound, the sound level tries to increase but is constantly turned down. When I stop trying to intervene, the sound goes back to zero.
After about a minute, I'm able to increase my sound again and the sound level will maintain normally at the set level.

I'm not running any other programs. And even if I kill mozilla, it doesn't fix this. I still can't increase the sound level, for a minute or two.

I am running Win Pro 7/64 SP 1 on the W530, and Win Ultimate 7/64 SP 1 (?) on the T61p. I have a Jabra GO6470 system that integrates with my computer, and there's a bunch of Jabra drivers installed. The other suspect is the non-lenovo approved nVidia driver. I installed the latest for the K2000M, which has some audio drivers that interfere with the Realtek and Jabra drivers, and so I disabled the nVidia HD audio.

Any ideas on what's causing this?

[RealBlackStuff]

Since you pretend you know everything, I suggest you figure this out all by yourself.