In addition to my earlier post detailing how to get Aero Glass working I've found that making a change to the BIOS on my machine has ensured that I can now reliably use an external monitor and also project.

The setting in question specifies whether the computer should attempt to automatically detect the presence of an external display or not. My system (a Toshiba M4) defaulted to "automatic" detection - this was the root cause of me not being able to project. I changed the setting to "always output" and hey presto I've been able to reliably project / drive a monitor ever since