I am also using Bit defender in my PC but i never face these type of problem in my PC, it provide deep scanning,automate updates and i am totally satisfied with it !!
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bitdefender antivirus 2011 download

i want to say one more thing... sometime in windows 7 notification windows shows that bitdefender is disabled... and when i tried to enable it nothing happens.....
but after restarting the computer this was automatically gone....

plz check this issue and send me solution.....

Hi basant.ece!  I verified this issue you reported with the support team-  and it seems unusual.
What they recommend is to:
1. please verify that you uninstalled  any other security solution that could conflict with BitDefender;
2. try to stop any application with real time access on files  (like a defragmentation process or a back-up process);
3. if the issue persists, please send our support a file that you tried to scan with the mention of the scan time;
4. we are working on the option of manual product updates for BitDefender 2011, they will soon be posted here:
http://www.bitdefender.com/site/view/Desktop-Products-Updates.html

Please don’t hesitate to send me a direct message or to contact our support team directly:)
https://myaccount.bitdefender.com/site/Main/view/support-phone-hho.html

best,
Raluca

i want to add one more thing plz say bitdefender developer to provide manual update..... link   

there is one problem with bitdefender total security 2011 , when i do manuall scan from right click menu it takes too much time to calculate estimated time for scanning..... as a result too much delay in scanning process.... plz check this bug of bitdefender 2011.....