Just follow these steps.

1. David said: “It seems that SL 4 b places the following in a hidden location /private/var/db/receipts:
   com.microsoft.installSilverlightPlugin.bom
   com.microsoft.installSilverlightPlugin.plist
   com.microsoft.installSilverlightPluginDebugApp.bom
   com.microsoft.installSilverlightPluginDebugApp.plist
   com.microsoft.installSilverlightPluginDebugFiles.bom
   com.microsoft.installSilverlightPluginDebugFiles.plistThe solution is to run this in Terminal. Copy and paste into terminal, then press Return.
   sudo rm /private/var/db/receipts/com.microsoft.installSilverlightPlugin*

   If you are uncomfortable with Terminal you can remove them by hand. In Finder select Go to folderfrom the Go menu. Cut & paste /private/var/db/receipts into the dialog box and press return.”

2. Kreftovich says: “The annoying SilverlightDebugProxy on startup is gone. Had to run this commands in terminal
   rm –rf ~/Library/Application Support/SilverlightdebuggingConfig1.0
   cd ~/Library/LaunchAgents
   launchctl unload ~/Library/LaunchAgents/com.microsoft.silverlight.debugproxy.plist
   rm ~/Library/LaunchAgents/com.microsoft.silverlight.debugproxy.plist
   First command didn’t work so had to doit manually but all others where fine.
   Thanks a million everybody. Peace”