Robot Structural Analysis Professional: Extension Error

I am having a problem with my Robot Pro 2011. I am trying to install the extension for robot (robotextensions2011.exe – 212Mb). The setup gives me the following error: “robotextensions2011.exe – 212Mb”.
What could be causing this? More importantly, how can this be fixed?
Thanks in advance.

Robot Extensions for Autodesk Robot Structural Analysis 2011
Robot Structural Analysis 2011 or Robot Structural Analysis Professional 2011 is not installed on this computer!
Please install one of those programs first.
