There really needs to be a sticky on what Script Shield and File Shield do and what they don’t do

http://download801.avast.com/files/marketing/materials/whitepaper_scriptengine.pdf

Script Shield scans primarily Windows Script Hosting (WSH) scripts

WSH is a language-independent scripting host for 32-bit Windows platforms. Microsoft provides both Microsoft Visual Basic Script and Java Script scripting engines with WSH. It serves as a controller of ActiveX scripting engines, just as Microsoft Internet Explorer does.
[url=http://support.microsoft.com/kb/188135] http://support.microsoft.com/kb/188135[/url]

File Shield scans files and not scripts related to WSH.

Since all 32bit versions of Internet Explorer use the WSH you should see Script Shield activity when using them both internal and those on Webpages that you have visited. I don’t know about IE9 x64 but to my knowledge Firefox does not use WSH so therefore you will not see as much activity in Script Shield when using Firefox. What activity you will see will be related to WSH and Windows operating system.

If you are using Firefox you will need to use NoScript to protect you from malicious scripts for the reason I stated above.