You with o2 or BeBroadband or have a router like this?
Command Prompt>Telnet 192.168.1.254 (I think), User+Password (If O2 Username is SuperUser Password is O2Br0ad64nd ) type connection bindlist look for a line that says GAME(UDP) then type Connection Unbind Application=GAME(UDP) port=27010-27011 (Or whatever ports are shown in your list.
Then go try. Works perfectly for me. Occasionally have to redo it if my router resets.
Edit.
The TF2 Update list doesn't list everything. The Force a Nature now fires 50% faster instead of 60%, has -10% damage rather than -25%, and has 20% more bullets per shot rather than 25%. Sandman actually reduces health by 30, not 25 like the list says. With Sandman equipped throwing the ball is done by secondary fire so you can still primary fire to melee.
Edit 2.
Phal's post says The Sandman reduces health by 30. In my update list it says 25. Maybe they altered it just before he got updated; I got it almost immediately as it was released.