I'm having problems painting. I can fill my mesh with colour and that works perfectly, however if I try to use the brush nothing happens. I've tried this at work (Windows 7 pro, brand new Intel Graphics Cards) and at home (iMac 2013) and the same thing happens. I've tried changing the value in the config file on the mac from 0 to 1, as some people suggest, but this made no difference (oddly enough, the install on Windows has no config file...).

I'm wondering if there is something really basic I'm not doing.

It's what I don't know I don't know is always the problem!