Skype Randomly Mutes Microphone

[Petie]

If you've got the option it could also be useful to test either an external audio card or USB microphone/headset, since those don't rely on the internal hardware or drivers, that should tell you pretty easily if the problem is specific to your audio device or if it's more widespread.

It happens with both my computer's internal mic and a separate USB mic.

He's actually already tested that aspect which is why, combined with a bit of research (and the post he deleted), I suggested checking a bit more thoroughly for malware.