We've seen this occur when the preview release of Internet Explorer 9 is installed. To resolve this problem, disable GPU rendering in IE9 by following these steps:
- Open IE9
- Click the gear icon at the top right
- Click "Internet Options"
- Switch to the Advanced tab
- Checkmark the option labeled "use software rendering instead of GPU rendering"
- Press OK, then close IE9
The next time you run FeedDemon, it should start normally.