I have had an issue where web browsers (I tired Internet Explorer 10 and Firefox 23.0.1) would not load in Avast Sandbox. This was resolved by uninstalling the Trusteer Rapport application.
This isn’t necessarily a problem to me as the only reason that I installed Tusteer Rapport was because my bank recommended it. I have just posted this information incase it is of use to anyone, or anyone knows why this issues exists.
