Reporting Services Configuration Manager: "Invalid namespace"

http://support.microsoft.com/kb/960374/EN-US

Above will work for 2005 as well.

Method 2: Add a WMI namespace
Add a WMI namespace that corresponds to the namespace that the SQL Server 2008 Reporting Services Configuration Manager tool is trying to use. To do this, follow these steps:

Note This procedure refers to a sample instance that is named "SQL2008."

Locate the Reportingservices.mof file for the SQL Reporting Services 2008 instance that is named "SQL2008." By default, this file is located in the following folder:
C:\Progam Files\Microsoft SQL Server\MSRS10.SQL2008\Reporting Services\ReportServer\bin
Save or copy the Reportingservices.mof to a file that has a unique name, such as Reportingservicesalt.mof.
Open Reportingservicealt.mof file by using a text editor, such as Notepad.
On the Edit menu, click Replace.
In the Find what area, type the changed instance name, such as RS_SQL2008.
In the Replace with area, type the unmodified instance name, such as SQL2008.
Click Replace All.
Save the file, and then exit Notepad.
Open a command prompt, and then move to the same folder that you used in step 1.
Type mofcomp reportingservicesalt.mof, and then press ENTER.

NOTE:- it may need not to be same as file name reportingservicesalt just check and execute mofcomp reportingservicesalt.mof from folder location.


Note If the reporting services instance name contains an underscore (_), a dollar sign ($) or a number sign (#), you have to use method 1. Or you have to reinstall the instance.