You know the one I'm talking about:

SqlError: The backup set holds a backup of a database other than the existing 'Pro_SSRS' database. (Microsoft.SqlServer.Smo)

For some reason, if you tell SQL Server to overwrite the existing database (look below), the restore works like a charm. The database that I was restoring to had the same name as the backup file, and I'm not so experienced with SQL Server as to know what other (if any) mistakes I was making.

Step 1: click on Options tab; Step 2: check the 'Overwrite existing database' option.