Ha! G string was my nemisis! I played an unwound G for quite some time on my acoustic because I broke wound ones so often. It did no favours to my guitar, though it has withstood the years quite well. (It was like a peice of aircraft cable :P)

Anyway, I had a bad bridge slot, so nobody else will likely have the same problem.

Getting to the point, ksturgeon, I would suggest at the very least, purchasing a new set of strings asap. Generally what comes from the factory is often crap. Perhaps a "light" set (starting with 11 on the e) would be a good place to start. You could possibly go up to "medium" (13's) with no nut adjustment.

I'd recommend 11's. d'Adarrio. They will be easier to play starting out anyway then a heavier string and you should not have to worry about damaging a nut or strings binding in the slots.

When to change is mostly a matter or your personal taste and how often you play. Some folks have a high tolerance for "dead" strings. You will know when it is time for you. Esp once you hear the difference after a set or two :)