My status bar icons (NoScript and IETab) both disappeared after I installed HP Smart Web Printing 4.60 on FireFox 3.5.7.
Disabling and restarting Firefox resolved this.
[RESOLVED] NoScript icon is missing in bottom toolbar
Re: [RESOLVED] NoScript icon is missing in bottom toolbar
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 GTB6 (.NET CLR 3.5.30729)
Re: [RESOLVED] NoScript icon is missing in bottom toolbar
I had the same issue--no script icon had disappeared and wouldn't reinstall. The solution was to uninstall "McAfee SiteAdvisor". Once I went to Control Panel-->Programs-->Uninstall Mcafee Sitadvisor, Firefox restarted and Noscript was back.
Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3 ( .NET CLR 3.5.30729)