FWIW I just got this one or similar on today's nightly, Mozilla/5.0 (Windows NT 6.0; rv:2.0b7pre) Gecko/20100916 Firefox/4.0b7pre ID:20100916041016
Error: uncaught exception: [Exception... "Cannot modify properties of a WrappedNative" nsresult: "0x80570034 (NS_ERROR_XPC_CANT_MODIFY_PROP_ON_WN)" location: "JS frame :: chrome://global/content/bindings/autocomplete.xml :: onxblpopuphiding :: line 847" data: no]
FWIW I just got this one or similar on today's nightly, Mozilla/5.0 (Windows NT 6.0; rv:2.0b7pre) Gecko/20100916 Firefox/4.0b7pre ID:20100916041016
Error: uncaught exception: [Exception... "Cannot modify properties of a WrappedNative" nsresult: "0x80570034 (NS_ERROR_ XPC_CANT_ MODIFY_ PROP_ON_ WN)" location: "JS frame :: chrome: //global/ content/ bindings/ autocomplete. xml :: onxblpopuphiding :: line 847" data: no]