Here are some places to start:
1. The green wire going to A4/5 is only suppose to have 1/2" of its jacket stripped off. It looks like much more jacket has been stripped off. If that wire touches any other terminals, problems will follow. I would redo that connection.
2. The capacitor between terminals 9 and 10 is in backwards.
3. The solder joint at terminal 3L looks like it needs just a bit more solder. Try to heat just the terminal strip itself, then let the solder flow into that lower hole.
4. The 220uF capacitor at 12/13 (where the 270K resistor is) looks to have one lead that isn't soldered to the terminal strip. This will result in a noisy amp.
I am absolutely elated that you came here for help! If your voltages don't return to normal with that 100uF cap flipped around, you can try measuring the voltages without the cap in the circuit (if they straighten out after that, then the cap needs to be replaced).
Also give close inspection to those 2.49K resistors on the headphone jack. With that cap in backwards, it becomes seriously angry and can really give one of those 2.49K resistors a beating. One will be noticeably darker than the other if this has happened, and it may no longer measure as 2.49K.
-PB
