STR: 0. Fire up a debug mozilla-central debug build. (w/ empty profile) 1. Drag and drop a file (e.g. an empty .txt file) onto the Firefox window. ACTUAL RESULTS: Assertion failure: mInitialized, at ../../../mozilla/widget/xpwidgets/nsTransferable.cpp:447 Likely a regression from http://hg.mozilla.org/mozilla-central/rev/93e55dcf0e2e for bug 722872 which added that assertion and was merged to m-c 2 days ago.
See also bug 769440, about Addon SDK hitting this same assertion during an automated test. (May end up being the same underlying issue.)
Looks like a dup of bug 769653.
Agreed, based on bug 769653 comment #2. Thanks!