I resolved the issue by simply adding safe control entry in my web.config file.
<SafeControl Assembly="Microsoft.PerformancePoint.Scorecards.WebParts, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" Namespace="Microsoft.PerformancePoint.Scorecards.WebParts" TypeName="*" Safe="True" />
Hopefully it will resolve your issue as well.
Thanks,
Ashish