Just figured out a bug/conflict that’d been niggling at me for a while.
A few months back, the Insert/Edit link button (on the visual editor page of WordPress) stopped working under Firefox.
I’d just done a whole bunch of site upgrades, so I figured it was just a temporary wordpress bug.
However, several updates later, and it’s still there – and on a couple of different sites, so I thought I’d investigate a bit further.
After much digging around, I figured out what it was.
Adblock Plus blocks the javascript because it creates a popup window called “tinyMCEPopup” – and of course, the anything called “popup” is evil.
To fix this, ensure that Adblock Plus is set to show in the status bar. (Tools | Adblock Plus Preferences – then when the window opens, under Options, check that “show in status bar” is ticked)
Then you’ll get a little red ABP stop sign in your status bar, you can then right click on that, and select “Disable on [yourdomain].com.” When you do that, it’ll go grey, showing that your domain has been whitelisted, & Adblock Plus will stop screwing with it.
Once the ABP icon is grey, you’ll need to refresh the page, but after that, everything will be hunky dory.