Works OK for me, rjb.

But maybe not for you, yet.  Because of Mozilla policies, BookMacster needs to install a different Firefox extension for each Firefox major version.  (That's one of the reasons why the BookMacster package has grown to 21 MB in size … the current version contains 4 Firefox extensions, for Firefoxes 4, 5, 6 and 7).

But BookMacster only checks the extension, I think, when you launch it, attempt an Import, or an Export.  Try to quit and relaunch BookMacster.  Does it offer to upgrade the Firefox Add-On?  (Maybe we should add a timer for BookMacster to test its Firefox version while it is running, every 10-20 minutes or something like that.  We'll try and think of a better way, though.)

If that doesn't work, click in the menu BookMacster ▸ Manage Browser Add-Ons.  "Test" and if necessary "Install" or "Upgrade" the Firefox extension.

And then there's one other thing, but this is nothing new, which is that Firefox only shows BookMacster's widgets when a browser window is open.

Let us know what you find.