I can confirm that mine GUIMiner isnt working either. Getting tons of:
2012-02-04 22:07:01: Listener for "PH1": pit.deepbit.net:8332 04/02/2012 22:07:01, Unexpected error:
Can you try any other miner like Phoenix or cgminer and tell us if it's working or not ?
Phoenix using guiminer seems to be working but I can confirm that (using guiminer) that the default get the error: "2012-02-04 15:03:57: Listener for "Default": pit.deepbit.net:8332 04/02/2012 15:03:57, Unexpected error:"
This was working yesterday but today the guiminer is not working without having to switch to Phoenix.