I'm running Windows 10 and I've had this issue with my Soundblaster Omni 5.1 for sometime now where the mic would stop working randomly when I'm chatting with my friends on Teamspeak. I continue to hear just fine with my headphones (which are connected to the Omni as well) but the mic doesn't transmit anything.
Initially, I was using the built-in mic in the Omni but recently I've switched to using a ModMic which is connected to the mic input.
Usually I restart TS and that will solve the issue, however the last couple of times I've needed to disconnect the USB from the computer and plug it back in. (it is not connected via a hub.)
I don't believe the issue is TS, as when it occurs I have gone to Windows Sound and tried to listen to test the mic and it didn't work. I also tried in the Soundblaster software, which didn't pick up any sound from the mic either.