Vielleicht kommt dein Router nicht mit den UPnP von Vista zurecht. Schau mal nach einem Firmware Update.
Ansonsten hat google noch folgendes gefunden :
# Start -> All Programs -> Accessories -> Right click Command Prompt -> Run as administrator.
# Copy the following exactly (without quotes): "bcdedit /set loadoptions DDISABLE_INTEGRITY_CHECKS". Right click on the title bar, go to Edit -> Paste. Make sure what was pasted is correct, then hit enter to execute the command.
# Reboot the machine
# Now the first time you load PeerGuardian you will see a message like the below. If you performed the above steps correctly, it is safe to ignore this. You can make sure by turning on Show Allowed under settings, and making sure an IP scrolls by when you visit a website.