I've been able to save stuff if I go fast enough, but to answer your questions;
1. No, my biggest map file is 55 kb.
2. I haven't done anything with the map editor while saving.

I just ran a few more tests, and I found that about 30 seconds after I click save it throws that error. I think I was having trouble with it before because it was taking a while for me to find the directory I wanted to save to, but now that I have it selected it saves there by default and I just have to type a file name.