Thanks Garran and Paul. But the problem is not on my own computer. The problem is on clients side, I cannot ask him to alter his security settings. And if I could, i don´t know if he does know how to do it.

On the other hand, I have been asking, and a Verizon certificate here in Spain would cost around 400 Euro a year. Thats much too expensive for the basic software I am developping.

So, I don´t know what to do.

Do you think there is a specific snippet in the code that brings Avast to open it in the sandbox, and if so, is there a way to know what piece of code it is, or is it the normal bahaviour when there is no certicate?

Many thanks for your help