Regarding the ' - it is a shortcut key for something called QuickFind (I know not from where it came!) which pops up if I select ' outside a reply box. Clicking inside the box works as normal. The search box on mine comes up in the taskbar.
I get the popup on any web page. It appears to be a piece of freeware. It's on 3.5.5 as well, gg - definitely something 'Firefox'. Not listed in add-ons or plug-ins. Found
this and
this