Toolbar Buttons has just been updated to 0.3.0.5 this is several versions newer that the one currently found on addons.mozilla.org since there is always a delay in the update there.

This version contains a number of bug fixes to the language packs, along with changes to some of the bookmark button icons, since they were all using the same image.

The next version a plan to reintroduce support for Firefox and Thunderbird 1.5 which was dropped because some of the buttons of 1.5 don't work in 2 and vice versa. I working on a method around this.