Administrator privileges

Someone other than myself recently worked on a 2003 SBS while
I was on vacation. The server was set to back up to another
computer in my office and worked fin for several months. Now it
says it can’t find that computers volume and that I don’t have
sufficient privileges to access this computer (or other derivations
of insufficient privileges). I can’t manage or log on to the other
computer from the server. I checked all the IP settings and the
other computer functions fine on the network. I am logged on
as an Admin, what could be wrong?
Thanks