UA-25EX Electric Guitar MONO

Hey everyone. I could really use some help. I have a Macbook Pro 2.8 GHz Intel Core 2 Duo. I'm using Logic Pro 9.0.2 on it.

First off, anytime I plug in any mic or plug in an instrument the signal is so low. Like barely see it half the time. I turned up the volume on the guitar, and the gain on the UA-25, course. I would crank them up till it distorted, but still would see very little to no signal getting to Loigc. 

One day, I was playing with an electric guitar in, and when i hit the mono switch the signal problem was gone! Coming in clean and fantastic, except it was all out of the right side. Also, if I tried to pan the signal over to the left, it would just decrease in volume not move the sound. I can't figure out why this is happening, so any and all suggestions would be really helpful.
Thanks!