Bitdefender Antivirus Reports That It Might Be Out Of Date.

I have Bitdefender anti virus 2009 and windows vista home premium 32 bit. Few days ago the windows security alert started to show a critical warning "Bitdefender Antivirus reports that it might be out of date". When I update the software it updates normally and shows that the last update date is today's, but this windows alert is not going.

An interesting thing to add is that last week the bitdefender started to ask for reboot to configure updates about three times a day for three continues days.

please help me sort this out.