Recently I encountered an odd problem: after initiating a session I was presented with a new window which terminated immediately. The return code of the rdesktop program was 141. Googl´ing for this return code I found that it is related to the (terminal server) license. Indeed, it turned out that the terminal server was unable to contact the license server and hence denied new connections (existing ones were however maintained, which - and the fact that for the first 90 days the license is not verified - misled our IT staff initially).
I think, this would have been easier to resolve, if rdesktop would report errors more verbosely (try to convince your local IT admin that something is wrong with his server when all you have is some blog entry ;-)