Bitdefender Slows Itunes Downloads

Hi

I have a 200 MB connection I usually download very quickly. On iTunes, it can take several hours to charge 20 or 30 MB.

If I disable the firewall, antivirus and privacy control, it changes nothing. But if I prevent BitDefender services to work (which is very easy to do), iTunes starts to download very quickly. If BitDefender manages to reestablish its services, iTunes starts again to download slowly.

I authorized iTunes, the program Apple update, Bonjour and all Apple programs that I could find for the firewall. I even excluded the iTunes program and update of the AV, it changes nothing: I must stop BD services if I want that iTunes download at a normal speed.

Thanks for your help !

Richard