Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9pre) Gecko/2008081217 Minefield/3.0.2pre Steps to reproduce: -> Install the NewsFox Extension -> Start Firefox with this Extension installed --> Error: uncaught exception: [Exception... "Component returned failure code: 0x80040154 (NS_ERROR_FACTORY_NOT_REGISTERED) [nsIRDFService.GetDataSource]" nsresult: "0x80040154 (NS_ERROR_FACTORY_NOT_REGISTERED)" location: "JS frame :: chrome://newsfox/content/livemarks.js :: anonymous :: line 148" data: no]
I think this happened because NewsFox was unable to determine the userAgent and thought Minefield was Firefox 2 or less(hence the rdf bookmarks). [Not using nightlies so can't tell.] This is fixed in 1.0.4beta1 at http://newsfox.mozdev.org/installation.html#beta. Comment: It would never have happened if Minefield set general.useragent.extra.firefox to 'Minefield/x.x.x Firefox/3.x.x' similar to Flock's 'Firefox/x.x.x Flock/x.x.x'.
Closing as invalid (no Firefox Bug) also per comment #1 fixed in 1.0.4beta1 of the Extension.