Error on startup or AutoCAD is not installed properly. Please reinstall immediately in AutoCAD Civil 3D 2011

Issue
When you launched the application, it immediately closes. The following error message may or may not be displayed:
This version of AutoCAD was not installed properly and some features may not run correctly. You should reinstall AutoCAD immediately to make sure all features are working properly. Do you wish to continue anyway?
Solution
We've discovered one source for this issue that stems from a bad registry entry in the HKEY_CLASSES_ROOT\.png key.

There have been cases where the value in the Content Type key contains a leading space.

In some cases, simply removing that leading space in the value resolves the issue. We don't know how that value is getting set with a leading space - it is not being done by Autodesk - nor do we know if removing that space affects any other applications, however users who removed the leading space did not report any other issues.
1. Run REGEDIT
2. Navigate to HKEY_CLASSES_ROOT\.png
3. Modify the Content Type value to remove a leading space (if one exists)
If this did not apply to your system or it did not resolve the issue, these errors may indicate a corruption of the Microsoft® .NET Framework. This operating system component is required for several AutoCAD features, including the Properties Palette, Layer Manager, Ribbon, Menu Browser, Tooltips and other features.
To correct this issue:
1. On the Start menu (Windows), click Settings > Control Panel.
2. In Control Panel, double-click Add or Remove Programs (Windows 2000/XP) or Programs and Features (Windows Vista).
3. Uninstall all versions of .NET Framework, beginning with the newest version first.
4. Reinstall only the version of .NET Framework required for your software version. Refer to the list below for AutoCAD requirements. For vertical products, consult the product installation literature for the required .NET Framework version.
• AutoCAD 2008/AutoCAD LT 2008 requires .NET Framework 2.0
• AutoCAD 2009/AutoCAD LT 2009 requires .NET Framework 3.0
• AutoCAD 2010/AutoCAD LT 2010 requires .NET Framework 3.5 Service Pack 1
• AutoCAD 2011/AutoCAD LT 2011 requires .NET Framework 3.5 Service Pack 1