So your problem is fixed now?
no
so I uninstall the version 5.0.677 , reboot the pc;
then I reinstall version 5.1.864 and reboot;
same thing
if I try to close or clic on "annuler" or "continuer" of this box the pc freeze;
when I insert an empty floppy disk in A and clic on "recommencer"(try again)or clic on the [X] the message box disappears and FirefoxPortable open and work normaly.
This doesn't produce with the previous version 5.0.677 of Avast;
so there is a bug in the 5.1.864 version.