On my setup (Firefox 26 and Paste Email Plus 4.1) I have noticed for some time that the label is missing on the "Remove Bookmark" button in the small window that opens when you click the gold star in the address bar. For me the button has a blank label, in two Firefox profiles where I use Paste Email Plus.
Maybe someone else can reproduce the problem.
1 Click on any bookmark that you have in your bookmarks list.
2 When you see the gold star in the address bar at the top of the window, click on the star to open the window.
3 There should be a label that says "Remove Bookmark", but for me the label is missing from the button if Paste Email Plus 4.1 is Enabled.
4 If the extension is Disabled (and Fx restarted), then the label shows on the button.
I have added Paste Email Plus to a Firefox profile that has no other extensions installed in it, and get the same result.
If I Disable the extension, the button's label shows as expected.
I haven't tried Disabling plugIns, so it's possible that a plugin might be involved with this.
It's easy enough to check this.