As a test, please disable McAfee. It has caused problems.

IsabelGibson said

After the 07/07 update, many (but not all) pages that previously worked fine are now timing out and need to be reloaded to load (for the first time, as it were). Started by clearing cache, then checked for malware, and ended by reinstalling Firefox. I copied my profile rather than starting from scratch with extensions (only running about 5). All these problematic pages open fine in IE. Any ideas? Many thanks.

Thanks, that was quick! The worst-offending site opened fine with McAfee disabled - without any other security I'm reluctant to do a longer test! Whither now, o wise one? Or do you mean just to disable the Site Advisor plug-in?

Unless someone shows up here with advice, contact McAfee support.

But first try this;

http://service.mcafee.com/faqdocument.aspx?id=TS100162 How to uninstall SiteAdvisor

To disable it: Type "about:addons" in the Location bar Find the extension and click on its "Disable" button

Thanks kindly, Fred - will try that.