This has happened to me a couple of times:
-While using "Edit 2" to modify a problem file, for various reasons I ended up with webwork "timing out".
-When I returned to work on the problem which was still up on my computer screen, the first thing I did was click to "Update" the file and I was sent to the login screen.
-After I relogged in, the file that was saved had all of the special characters converted to html codes.
Here's an example of part of a file after the save:
FYI: We are using: theme: math3 | ww_version: 2.8 | pg_version: 2.8
The most recent upgrade was done on Jan 31, 2013.