After installing the web part for PerformacePoint Monitoring Dashboard Viewer in Sharepoint, I got the following error:

Parser Error Message: Could not load file or assembly ‘System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35’ or one of its dependencies. The system cannot find the file specified.

This error kept throwing me off and I could not understand the reason. Finally, I figured out that I needed to download and install the ASP .Net 2.0 AJAX Extensions, Microsoft says you dont need it if you have ASP .Net 3.5 installed, but it turns out otherwise !

Click here to download Microsoft ASP .Net 2.0 AJAX Extensions

Did that and viola – back in business again…