SharePoint 2007 : SSRS configuration issue

Hi Guys,

I'm working with integration of SQL Server Reporting Services (SSRS) into SharePoint 2007, I've setup the Reporting Services Configuration Manager and installed Reporting Services Add-in for SharePoint in WEB and INDEX Server.

I came to a point where I able to open http://DBServerName:8080/reportserver and the able to see list of web application.

However, I having problem on open "Set Server Defaults" setting in Central Administration.

Once it is click, it hit error page below saying having connection error to report server (in my case is DB Server)

so my question is any idea what is wrong? and where should I start troubleshoot?

thank you in advanced.