When you can't download updaters or when you receive an http 404 or http 403 error change the update server by one of these:
http://update.bitdefender.com
http://upgrade.bitdefender.com
http://upgrade1.bitdefender.com
http://upgrade2.bitdefender.com

How to change?

For the 2008 products:
Start BitDefender 2008 by double clicking on the red BitDefender icon near the system clock once you are in the BitDefender Security Center press on settings,click on update,settings,primary update location settings and change it or keep the default server. Change also the alternat update location settgings. Don't forget to press on apply.

For earlier products:

Start BitDefender by double clicking on the red BitDefender icon near the system clock. Press on update,settings,primary update location settings and change it or keep the default server. Change also the alternate update location settgings. Don't forget to press on apply.

If the problem still persists you can download the updates here.