I run a small interactive agency, half my time is doing business and half coding. The single most difficult thing I have to deal with is the context switching. When I'm "taking care of business" its a crap load of little things which need to be done, as opposed to code which I need to do in a large multi-hour block. I can never intermingle the two or the coding just doesn't get done. My business partner (creative director/designer and runs our NY operation - I'm in SF.) can now tell on the phone if I'm in "coding" mode and has learned to leave me alone.