How did I find this problem? There was a power outage, my Workstation in the basement rebooted and hanged at POST. I turned on my Dimension upstairs as usual when I came back home, and tried to remoted to Workstation, I got this error. I went to the basement, let the Workstation boot up and logged in, didn’t see anything unusual. Have read a lot of articles and posts, finally, I found the IP address I thought is used by Workstation is actually used by Dimension – I was literally connected to the console of this computer! 
If you really have a problem in connecting to your Windows server or other machine, the following links may give a hint.