Apparently, it seems to work with IE - not sure if its firefox though, as exiting a dungeon still takes ~ 1-2 minutes. Sorry for the DP btw, but I thought its better to tell you.
Aeq has taken a look at your savegame and thinks he's managed to optimise the general loading process as a result - hopefully it'll work better come friday!
It's probably falling over in FF due to memory pressure issues. Hopefully that's also something that has been made slightly less horrible.