Cannot Connect Using SSMS to Local SQL Server 2008 R2
As I posted in the comments, a couple of possibilities exist for that error, mainly lack of memory for additional TCP connections (generally in conjunction with 32-bit OSes), or lack of TCP ports. Both issues (and possible solutions) are outlined here on the SQL Protocols blog:

Understanding the error "An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full."