No, Sir. I have meant that there are 13 different servers and 13 different instances. That means every server has only one single instance that is default "MSSQLSERVER". I can remotely access all of the 13 servers. I can also connect to 12 instances through SSMS. But in one server, it throws that error. Actually the word would be "office" not "work station". Sorry for the mistake.

I have not touched any memory configuration. All default values are set. I am not running any .net application just want to connect and work through SSMS.