For a while, the new tab (the +) button and the Ctrl-T shortcut for my Firefox 3.6.13 no longer worked. This happened suddenly and I didn’t remember what new software I installed to cause the problem. It was frustrating to have a non-functional button/command that I was so used to be using. I tried re-reinstalling Firefox but it didn’t help. So I decided to disable all the extensions and plugins at once. And it did the trick to bring the New Tab function back on. Of course, Firefox wouldn’t be too good without all the extensions and plugins. So now I had to figure out which one of the 20+ extensions and plugins is the culprit.
After 30 minutes of trials and errors, I finally root caused the problem to the Yahoo Tool Bar that came with the Java Standard Edition. By disabling the Yahoo Toolbar and enabling all others, I was able to bring my Firebox back from its handicapped state. I think Yahoo needs to do more software testing before releasing the software that adds more griefs than benefits.