Unable to share screen when external display is off

I recently switched from a Mini DisplayPort Adapter to DVI, which was attached to the tv using a DVI to HDMI cable, to a single Mini DisplayPort to HDMI cable. Now the machine goes to sleep whenever the TV is off.

Both the Computer sleep and Display sleep are set to Never, and have tried installing Insomnia. No go.

The machine is used as a media server for the rest of the house, so would prefer the machine to stay alive.

Any suggestions?

MBP

OS 10.6.8