I run a nVidia 9800 GTX+ at the moment and my monitor is 1680x1050 in terms of resolution. However CC has decided that I'm a dirty liar and 1680x1050 is unsupported.

Any reason why or can someone offer a solution?

Allegro's method of doing displays and CC don't always work well together.

Try slightly lower resolutions, and try setting it once, waiting for crash, then setting it again.

Alternately, set it manually in Base.rte/Settings.ini, though that's not 100% guaranteed to work.

It needs to be fullscreen. The window goes slightly outside the view when created and crashes if it's not.

I bet the Fullscreen thing is the issue. I can do 1680x1050 resolution quite fine.