Fixed, check 3rd post to find out how!
It loaded originally, then I made it fullscreen and made some graphics options from High to Med to improve framerate - when I next loaded the game I got (and now get everytime) the loading screen and then a dialoge box stating:
"This game has a minimum requirement of directx 8.0 to run properly."
On 6.2 on Mac
Update: Episode 1 runs fine, downloading Portal to test that.
Update2: Tried with command which works for Episode 1 =
"-console -heapsize 512000 -dxlevel 80 -width 800 -height 600 -window -novid +cl_drawmonitors 0 +r_shadowrendertotexture 0 +r_WaterDrawReflection 0 "
Still no luck[b]