Analog Inputs spew errors. Connecting 5v to reset fixes it. Eh?

I'm building a little MIDI controller and using Hairless to convert the serial. When I start hairless up, it gives me errors while I turn the pot. If I connect the 5V jumper to the reset pin and back, it starts working (sending out standard CC, just as I would like). That is, until I close and open the MIDI port again, in which case I have to move the jumper again. I don't get this - the analog pins normally work fine (I tried the analog read sketch) and moving the 5v jumper to any other pin and back doesn't work - reset only. I don't know what the reset pin's for, and I don't know if this is common, but it seems very odd to me.

Is my Uno broken? How can I fix this? Out of interest, what is the reset pin for?

The reset pin is to give access to an external reset button. Connecting this pin to GND then disconnecting it is synonymous to pressing the built in reset button.