I am getting the same error as Dave. I am sure the user/password are correct as they work with my other station using perl scripts. I did re-enter the information per Andrew's suggestion so I don't think it is that. I also noticed the error of unable to shut down the thread. This may be part of the issue as well.
I am using weewx 2.6.2 with 1wire hardware and OWFS.
Apr 23 11:15:25 raspberrypi weewx[1732]: restx: Wunderground-PWS: bad login; waiting 60 minutes then retrying
Apr 23 11:15:25 raspberrypi weewx[1732]: restx: CWOP: Published record 2014-04-23 11:15:00 EDT (1398266100)
Apr 23 11:16:12 raspberrypi weewx[1732]: wxengine: Received signal TERM.
Apr 23 11:16:12 raspberrypi weewx[1732]: wxengine: Shut down StdReport thread.
Apr 23 11:16:12 raspberrypi weewx[1732]: restx: Shut down CWOP thread.
Apr 23 11:16:32 raspberrypi weewx[1732]: restx: Unable to shut down Wunderground-PWS thread
Apr 23 11:16:32 raspberrypi weewx[1732]: wxengine: Terminating weewx version 2.6.2
Steve