Update deleted my tabs, made Close Tab buttons vanish and made entering an address into a tab not work

Question

Had some problems with Firefox being ridiculously slow yesterday, so I updated in the hope of speeding it up. Big mistake. Firstly, the 54 tabs I use for work were all replaced with Fast Dial screens. Assuming the add-on had gone rogue, I removed it, but am still having more problems.
All my tabs have gone mad. For one thing, any time I open a new tab, enter an address into the address bar and press Enter, or select an address from the Autocomplete menu, it does nothing. Only if I click a link that opens in a new tab can I open a new tab and get it to navigate to an actual address, but then, I can't access my other tabs until I've closed the new one. Also, all the Close Tab buttons have vanished from my tabs. To fix this, I have already tried:
a) Disabling hardware acceleration, which made no difference.
b) Starting in Safe Mode, which worked, so I went through my add-ons, narrowing it down. The problem appeared to be caused by Tab Utilities, so I disabled it, which solved the address entering problem. However, the Close Tab buttons were still absent, so I made the mistake of trying to find another tab management add-on that would be compatible with this version of Firefox. Found out the hard way that Tab Mix Plus and Tab Utilities Lite aren't, because the previous problem returned, but even now I've disabled both those add-ons (I think: can't double-check without closing this tab and losing the message), I still can't navigate to addresses in new tabs or look at any tab other than the most recent one I have open.
Any ideas what to do about this, please?

Answer 1

To check extension status, you can open a new instance of the Add-ons page by pressing Ctrl+Shift+a. This should open in a new tab next to the current tab. When disabling an extension, it often is necessary to restart Firefox before it actually is disabled (in that case, Firefox shows a link above the extension). To close that tab, you can use Ctrl+w.
I'm not sure why Tab Mix Plus would cause a problem using the address bar. Perhaps it is interacting with another add-on??
Could you describe the problem with the close tab buttons in more detail? Previously, it was possible to easily ''hide'' them on background tabs but now if the background tabs are wide enough they are always visible. There probably is a custom style rule (user style) to tackle that issue, but I'm not sure that's the problem you're having.
Not sure if this is relevant, but the Facebook Disconnect, Google Disconnect, and Twitter Disconnect extensions have been superseded by the (consolidated) Disconnect extension. They've switched from having individual icons inside the address bar to a single D button on the toolbar. Maybe that will help?