My audio input volume changes by itself

I use Maverick Meerkat. The sound worked perfectly the last time I had a conversation, which was on the 18th of Feb or so. Now I see that these problems occur:

- The input doesn't quite work unless I tinker it a little bit (change from Mic 1 to 2, and bring it back, and then leave it untouched for a while -- only then it may work, but not otherwise)
- Once it has started working, the volume slider (the input device volume, not the overall volume at the top) keeps changing its position automatically depending on how loud the sound output is in my headphone speakers

Would anyone have any idea about how I can at least stop the auto - movement of the input volume slider so that whenever the mic does work, it works consistently?

Thank you all in advance for your time and help.

Kushal