User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.8.0.4) Gecko/20060508 Firefox/1.5.0.4 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.8.0.4) Gecko/20060508 Firefox/1.5.0.4 Observers added to a nsiPrefBranch2 won't be notified when the PrefBranch is changed/removed using deleteBranch. The underlying libpref code won't issue the callback: http://lxr.mozilla.org/seamonkey/source/modules/libpref/src/prefapi.cpp#529 Although eg. the libpref code for clearUserPref will: http://lxr.mozilla.org/seamonkey/source/modules/libpref/src/prefapi.cpp#573 IMO, the optimal solution would be to use another topic cause the branch wasn't changed but deleted. Some notification must be there however. Reproducible: Always

Yeah, this hit me when trying to fix bug 349991...

(Filter "spam" on 'prefs-nobody-20080612'.)

Still open? I think tbhis is what I see. about:config doesn';t change when deleteBranch() is called, but re-opening about:config in another window shows the branch really has gone.