You have a problem when login in to AproPLAN?
You can find a few solutions in this F.A.Q like for example (empty the Silverlight cache).
In case it still doesn't works, you can always try to uninstall and install Silverlight again.
How does this works?
1. Click on Start (at the left bottom of your screen)
2. There you have to click on "Control Panel" under "Computer":
3. Now you can see a little screen with the title "Adjust your computer's settings"
You have to click on "Programs" - "Uninstall a program"
4. Then you will see a list with all your websites, you have to let them load, to then search for "Silverlight":
5. Once you have found "Silverlight", you have to click on it + at the top, next to organize, you have to click on "Uninstall"
To reactivate Silverlight you have to surf on this website :
Finally click on "Download now".