Make sure the external monitor supports the resolution you want to use.
Test different video cables.
Do not use any kind of video adapters.
I also recommend the following 2 links for resolution issues:
1099 isn't the latest version of the driver anymore. It's now 1130/A05. You can pick it up at Download File | Dell US. I wonder why Cedar Trail users can't get this same driver, but that's another topic for another thread.