MacBook Pro 2011 gfxCardStatus - Cannot change to integrated

My trusty laptop recently fail victim to the discrete graphic card failures affecting 2011 MacBook Pros:

https://discussions.apple.com/thread/4766577

I managed to get the computer to start up by following the advice to remove the ATI/AMD graphic card drivers. It has graphics problems everywhere, and is very very unstable.

Then I installed gfxCardStatus to force the computer to use the internal graphics card. However clicking on internal gives the error:

There is a dependency on "External display"

There is no external monitor connected, just a power cord. There is nothing in activity monitor that mentions external displays. In system preferences there is a picture of an external monitor, not my laptop screen. At the time my computer died it was connected to an external monitor.

This has affected a couple of people in the above mentioned thread.

Any ideas to force the integrated graphics card?