You can see where the villagers suddenly have new names.
I couldn't see where the villagers were renamed. I saw where a different game was loaded and they had new names though. What I thought was the same thing LadyCFII thought, that you switched to another slot (which is ok to do).
Just to help sort this out, are you running the games at the same time in different windows? I'm not sure even if this is possible, but I think I have heard of others running multiple games simultaneously. Perhaps they just were referring to those games that were not paused before they were exited (and hence they appear to have been running when resumed at a later time).
Is there anything you can think of that may have been unusual or out of the ordinary that might help track down and fix this?
Lastly, and this is a long shot, when was the last time your computer ran an antivirus sweep? Do you use AVG or Norton or.. ?