Using trunk builds, there are a lot of add-ons that are not compatible with it (or think they aren't). Because of this, a lot of users will check for updates to see if a more compatible add-on update is available. Right now, if they go to the Add-ons manager, select an add-on and choose to check for updates or simply select the "Find Updates" button on the add-ons manager, the following error will appear in the error console: Error: [Exception... "'Component does not have requested interface' when calling method: [nsIInterfaceRequestor::getInterface]" nsresult: "0x80004002 (NS_NOINTERFACE)" location: "<unknown>" data: no] This was found in Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en-US; rv:1.9a8pre) Gecko/2007090404 Minefield/3.0a8pre.