Yeah, try the default session as stated above.
But, above all...don't panic!
PatchMix is great once you get a handle on it.
Before you went and reinstalled drivers, etc...(updated drivers I hope) I would have suggested you check the output settings (OUT) and see if the headphone and monitor outs were enabled.
(Dock out 1,2,3 or 4 and Dock Headphone)
Once you get up and running, you may want a cleaner skin for PatchMix. I use one called "Lt Blue" that is much easier to focus on...better fonts and such.