Blocking to start Windows

I have a problem and I need your help. Let me explain!

Since few days, whenever I start my PC, it is impossible for me to open any programs. Moreover, it tells me that my antivirus: Antivir is disabled. And when I try to reactivate it, nothing happens, and if I look in the center, I have the software against malware disabled. Impossible to reactivate ... For everything to work, I only have one solution is to restart the PC in safe mode and then just restart normally, and strangely, it works again (antivir + programs).

I do not understand where is the problem, especially since it came at once. Virus? or others? Knowing that part Antivir, I also have Comodo and Spybot. All free software.

I'm on Vista with ASUS G50v. I already tried antivir reinstalled, but to no vial ...

Make a BIOS upgrade if possible, or failing memory problem.

http://support.asus.com/download/download.aspx?

The bios is up to date I believe, but I will check to be sure, thank you

A little update: I uninstalled Comodo, but not yet restarted, it takes too long to force .

It comes from an update to Comodo Internet Suite, it's Defense+, which blocks the execution of programs. Therefore, either change on security and off defense+ directly into the program, here's how:

Open the main window of Comodo Internet suite, and then in the "Defense+" click "Advanced" then "Defense+ setting", there is "Defense+ Security Level" on Disable and check "Deactivate the Defense+ permanently".

Reboot once done, the problem should be solved...