Unable to connect to the Report Server WMI provider.
As I was able to do this for another Report Server where SSRS 2008 R2 is installed, so the first thing I was thinking of is to upgrade SSRS 2008 SP1 with CU#5, but it made no difference.
The 2 servers are in the same domain, and can ping each other. Then i found the interesting thing is, i got the same error no matter what credential i put in, which lead me to think it might be a window firewall issue. I went to check the RS server's window firewall, it is ON! I turned it off, the problem went away immediately.
It turns out the following exception should be made: Window Management Instrument (WMI). Sharepoint did give out a very useful error message! Don't blame SharePoint.
