Be careful about search and replace.

In the than/then issue, I started noticing a lot of mistakes (you were thinking "than" when you meant "then"). You have to look at each one in context.

If you do a search and replace (which I guess I should've done, now that I'm a few days older and wiser), you have to click on each use of both words and then accept or reject. 

Do not just do a global switch.