I have the same issue. The Invert Mouse setting does not save once you exit MC and then restart. Minecraft 1.7.7
Anon, is that with a 1.4.5 generated Map? I have seen it in 1.4.x as well, but the map was generated in 1.3.x Not sure why that would make s difference though. I cannot reproduce in a 1.4.x generated map.
With 1.4.2 and a newly generated world I cannot re-create. It does still happen with my older world and MC version 1.4.2.
Uploading again as the last one didn't seem to work.
Can also confirm. Lost whatever is in slot 1 while trading with a Villager.