Hi from a newbie
I too have just been puzzled by this issue. In my case, I'd set the av to 'block and delete' infected files - and yes, it is Kapersky I use !!!
As I'd forgotten I had the settings to delete and not inform, I installed MIRC, only to find the 'exe' file had disappeared when I went to the install dir !
It is a trap, seemingly for users of Kapersky, which I like as an av, not as much as NOD32 mind you.
Obviously, I've skipped the deletion and all is well, as well as setting the av to 'block and inform user.
