Login to SQL Server 2008 R2 remotely
SSMS uses port 1434 and the UDP protocol.  This has to be allowed on the firewall, too.

Quote:


  When SQL Server clients request SQL Server resources, the client
  network library sends a UDP message to the server using port 1434. SQL
  Server Browser responds with the TCP/IP port or named pipe of the
  requested instance. The network library on the client application then
  completes the connection by sending a request to the server using the
  port or named pipe of the desired instance.


From here.