BitDefender 9 antivirus software

I purchased and installed BitDefender 9 antivirus software based on a good review in PC World magazine on 22 April 2006.  On 1 August 2006 I removed it from my computer.  Why? 

BitDefender updates itself and its antivirus files frequently.  However, after some updates BitDefender deactivates itself until the computer is rebooted.  Unfortunately, it does not tell you that it has been deactivated or that you need to reboot. 

The only way to know that something is amiss is to notice that the red BitDefender icon in the system tray at the bottom of the monitor has become gray.  If you open the program, you can see that the check box for turning the program on is unchecked, and the box can not be checked to turn it back on.  The only way that the program can be turned back on - and BitDefender never tells you this - is to reboot the computer. 

This means that the computer has no antivirus protection from the time BitDefender updates itself and you notice that it has turned off.  I think that this is unacceptable behavior for an antivirus program.