Fail to connect to server
Is this a named instance? If so, you need to ensure that the SQL Server Browser service is started. If it is not, you will not be able to connect.

Also, can you ping this server remotely? How about telnet to port 1433 (default port for the default instance)?

Check your SQL Server error log to see if there is any unusual activity and errors.

That's a start to troubleshooting this problem.