" In both places is the exclusion of firefox, both in the sandbox as in the general exclusions. Thanks for your answer "
So you are telling Miguelgrado, you got either Avast! Pro or Avast! IS because FF is excluded in AutoSandbox and Sandbox
But here you are telling me you have Avast! FREE which does not have Sandbox. Ok, it does not matter. It seems there is a little mix up with what you think is Sandbox in A!Pro and A!IS and what is Autosandbox in A!Free. This is what you are going to do:
1.) Download and save to your desktop aswclear.exe
2.) Download and save a fresh copy of Avast!Free
http://files.avast.com/iavs5x/avast_free_antivirus_setup.exe
3.) Open Avast! > Settings > Troubleshooting > Untick " Enable Avast! self-defense module ".
4.) Uninstall Avast! normally through Control Panel > Programs & feature ( Vista, W7 ) or Add and Remove programs ( XP ). Reboot. If you can not complete this step, continue with step # 5
5.) Even if you were able to uninstall Avast! in step # 4, it is important to run aswclear.exe in safe mode for any Avast! you may have had before and then for v. 7. Reboot into normal mode after uninstall.
How to run aswclear.exe in safe mode:
https://support.avast.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=1062#idt_02
7.) Reinstall fresh copy of Avast!Free and reboot.
Be aware. Avast! will offer Chrome during installment. Remember to opt-out if you do not want it.
After you reboot your fresh copy of Avast! free open Avast! and go to:
ADITIONAL PROTECTION > AutoSandbox > Settings > AutoSandbox Mode, and switch it to “Ask”. Then open FF. Any alerts ?