Weird bug about mMasterPrototype

[Jeremy Gillick]

I have an extension that uses an XCOM object (written in _javascript_) that causes these errors in a debug build: ###!!! ASSERTION: Missing master prototype. See bug 169036: 'mMasterPrototype', file /Users/jgillick/Build/Firefox/firefox-1.5/mozilla/content/xul/document/src/nsXULDocument.cpp, line 653 Break: at file /Users/jgillick/Build/Firefox/firefox-1.5/mozilla/content/xul/document/src/nsXULDocument.cpp, line 653 WARNING: NS_ENSURE_TRUE(mMasterPrototype) failed, file /Users/jgillick/Build/Firefox/firefox-1.5/mozilla/content/xul/document/src/nsXULDocument.cpp, line 654 WARNING: NS_ENSURE_TRUE(NS_SUCCEEDED(rv)) failed, file /Users/jgillick/Build/Firefox/firefox-1.5/mozilla/content/base/src/nsGenericElement.cpp, line 3827 WARNING: NS_ENSURE_TRUE(NS_SUCCEEDED(rv)) failed, file /Users/jgillick/Build/Firefox/firefox-1.5/mozilla/content/base/src/nsGenericElement.cpp, line 3827 My XPCOM object build a DOM structure on a DocumentFragment then holds it for the chrome code to use.  The chrome take the DocumentFragment node and clones it into the toolbar.  I know this seems like a lot of work, but it's how it has to be done in my case. Also, if I have the XPCOM code run, but turn off the chrome side, I don't get this error.  Does anybody know how an extension could generate this and how to prevent it? Thanks, Jeremy