Xamarin Studio won't start up

Hi all,
When I double-click my Xamarin Studio shortcut, or XamarinStudio.exe in C:\Program Files\Xamarin Studio\bin\XamarinStudio.exe, nothing happens apart from the mouse cursor flickering to busy and back again.

According to the exe properties, I've got version 4.0.0.0

I'm running Windows 7 32 bit.

Any thoughts/pointers?

Thanks,

James