slow graphics when laptop display is disabled

[René J.V. Bertin]

>graphics are unusably slow.  When the monitor of the laptop is enabled, 
>grahpics are at normal speed.

I can't answer your questions, but have you considered using this as a reason to get used to using a dual-head set-up?
FWIW, this is like the set-up I've been using for years now with my MBP: the laptop screen acts as a 2ndary screen when I'm at one of my fixed work stations, one I use for documentation windows, my email client's main window etc.

R.