Validating the game cache was the correct thing to do. Game seems to work again and the save files I couldn't play before now seem to work properly. Thanks for the help and quick response! Time to go have some fun now.
So, I'm about 2-3 hours into the game just exploring and doing whatnot. I did a quicksave and then went to eat, came back, reloaded and my entire party was invisible except for their weapons. Whatever, just a visual bug I thought, I could live without character animations. But, when I got into battle, I was unable to attack, cast spells or use skills. I was still able to be attacked. I tried reloading a previous save, and they're all the same. This entire playthrough is hosed.