mozilla-firebird tabbrowser extensions open in ... disabled

[Micha Feigin <michf@post.tau.ac.il>]

In the current version of mozilla with tabbrowser extensions installed
under the tabbrowser settings->context menu the open in ... options are
grayed out and I can't get at the "Open in new active tab" option for
right clicking on links option which I used a lot and really like.

Any ideas what happened to it and how to get it back? (I tried
uninstalling/reinstalling etc. but nothing seemed to help and google
doesn't bring up anything usefull).