yup, all the time, but if you keep your head in the space that this is a professional business then it usually helps. What I have started doing is making a schedule of things to do and trying to stick to it, as in
8-9 first thing check email, stats and boards
9-12 do boring repetitive tasks like avs/tgp/linklists
12-1 take lunch (make sure you get away from the PC)
1-5 do fun and exticing new tasks like research, set up a new site, etc
5-5.30 check email, stats and boards
5:30 - call it a day

this has really started to work well for me, it forces me to get the routine and boring stuff out of the way in the morning so that I can have more fun in the afternoons, plus it has stopped me from wasting all my time checking stats and webboards.

give it a try, it may help.

cheers,
Luke