“The server instance specified was not found. Please specify the server’s address and port.” Error
Dec 5th, 2005 by Sebastian
Yesterday I ran into this problem. I tried to deploy Web Parts package with stsadm.exe and then bam!!
“The server instance specified was not found. Please specify the server’s address and port.”
On Saturday everything worked like a charm, and on Sunday that error (don’t ask how I know it worked on Saturday and Sunday 
).
I didn’t do anything unusual. I’ve checked the Windows Auto update log, and it installed many updates on Saturday morning. I thought that it was it.
Anyway, what helped me is this post on Mohammed Jeelani’s Blog.
For me it was the first reason.