Make sure you have .NET 2.0 at least installed, you can get it from Microsoft's site. If you have it, it will show up in the Add & Remove Programs, don't know a better way to check whether or not you've got it.
It used to be included as part of the Impulse installer, but people were having issues with the old installer+downloader, so the SD devs changed it to be the "full" installer without needing to download during the install process, but then to keep the size down they removed the .NET distributable from it. At least, as far as I'm aware 
