I'm loosing maps!

1) I put a map
2) I click traverse
3) I enter portal
4) I get booted to login screen with "unexpected connection error"
5) I log back in
6) Map is failed and gone

Simply unacceptable.
This started yesterday and I checked the files for corruption: all files validated.
Pls give it top priority because the game is simply unplayable.

Thanks!