Open tab next to current tab not working

[bethel95]

Update: I just did a test where I disabled VT, restarted Firefox, and tried again. As expected, opening a new tab opens it next to the current tab. Here's where it gets interesting: Re-enabling VT without a restart gets VT working again without breaking FF. Unfortunately, VT reverts to the light theme (I prefer dark), and switching themes doesn't work without another restart (the tab background goes dark, but the text stays red, so it's unusable). As soon as I do the restart, tab opening is broken, again.

Original post: Starting about 3-4 weeks ago (possibly longer), all attempts to open a new (blank) tab or to open a link in a new tab caused the tab to open at the bottom of the tab list. Tab open setting used is for new tabs to open following the current tab. This was working after I installed this extension back in early Dec.

I'm using FF 36.0 (just updated yesterday) on Windows 7 Pro x64 SP1.