We recommend restarting Internet Explorer and performing a second update.

IF that doesn't work.......

I would try to REMOVE :

How can I remove Online Scanner from my computer?

Select Tools, and click Uninstall BitDefender Online Scanner v8. Restart Internet Explorer.

Reboot your computer and try installing again.

http://kb.bitdefender.com/KB162-nl--BitDefender-Online-Scanner-FAQ.html