[updated with net accounts command 20/2/2009] This can help diagnose and resolve the issue if like me, it was running fine and then it suddenly stops about 4-5 weeks after it all got started. My initial thought was that some update had changed things as the blog post here documented the initial setup where the same error was seen. The error once again looked like this: However checking all the same firewall and other settings revealed nothing. Finally I discovered that the user I had created had a password setting that meant the password had expired. Simple, yet checking from the command line is a right royal pain. To fix, these were the commands I used: net user <username> “<new or existing passsword>” /active:yes /expires:never /passwordchg:no net accounts /maxpwage:unlimited Simple, yet the cause of so much time trying to fix. Hopefully this will solve it for you too. Thanks David Technorati Tags: Microsoft , Hyper-V , Error , User , Password