While attempting to install .NET Framework 3.5 from Add Roles and Features fails with the error:  "The source files could not be found".  Attempting to install from the .NET 3.5 Framework install fails pointing you back to Add Roles and Features.

While attempting to restore files from an NTBackup .bkf file, you might find a reference to the Windows NT Backup Restore Utility for Windows 2008 Server and not Windows 2008 Server R2.  If attempting to install the former, you'll be greeted with an error which basically states you need to add the feature "Removable Storage Manager" but you are unable to locate this feature. 

I frequently use the command line for authenticating into various resources and every so often you get the following error:

"Multiple connections to a server or shared resource by the same user, using more than one user name, are not allowed"