When I try to call back to someone using sipdroid, it sends the number as it came, prefixed with '+'. It looks like PBXes can't handle such a number and hungs up the call.
Does the trunk used for the outbound call, support the (+) sign, or does it need to be removed prior from delivery to the trunk provider?
If this is the case, the dialing rule in the Outbound Route should be +|1NxxNxxxxxx for North American calls. Your dialing rule is missing the 1 in front of the N which only matches digits 2-9.