I now have a saving error appear everytime the game attempts to save bar the very first save directly after logging in.
The saving worked fine for hundreds of dungeon runs and i have no idea what may have changed since then
Since the saving took more and more time recently (~20s) and my second profile can still save (and much quicker) i would guess that it's also a file size issue. As i play from home my firewall isn't too restrictive nor had any problems with big uploads before. This problem appears in both firefox and internet explorer.