SQL Server Reporting Services 2008 on Vista : "RsClientController is undefined"

When working with the Sql Server 2008 Reporting Services web control on a Vista workstation, I was receiving a JavaScript error message: "RsClientController is undefined".

First, I thought to check the Handler Mappings, since I've experienced a similar problem with the .axd extension not being mapped properly. No luck. The mapping existed, and was set properly.

After investigating, and digging into the problem a little deeper, it would seem the solution is to add a mapping specifically for the Reserved.ReportViewerWebControl.axd

These are the steps:
1. Open Internet Information Services (IIS Manager)
2. Select your reporting site
3. Click on the "Add Managed Handler" from the actions

4. Enter the information for your new handler:

5. Click 'OK'

Resources:
Deployed reports have javascript errors?
Javascript Error When trying url access
SQL Server Web Report Viewer Issues on Longhorn/IIS7