At last! No thanks to Anastasia…

I just spent an hour on the phone with "Anastasia," an XM Listener Service Representative with a lilting Indian accent, who tried to convince me that I have a defective Zumo 550 and I need to contact Garmin. I assured her that I have all of the current Garmin software and have already communicated with Garmin.
I also pointed out that per this forum and also the BMW Motorcycle Owners of America forum, this is a widespread problem. Then Garmin must have several defective units in use, she opined.
She bristled when I suggested it was obvious she couldn't help me because nobody had told her how to solve this problem. All she could come up with was try another refresh.
(We all know the definition of insanity is doing the same thing over and over and expecting a different result.)
I told her about the fix of adding NavTraffic to the NavWeather. She put no credence in it, but we tried it anyway.
And it worked!
I had it on the Map screen during the refresh and the first clue I had that something was happening was the appearance of a Jackson County, Ark. flash flood watch box on the right side of the screen.
I went to the Menu, clicked the XM button and there on the next screen were buttons for XM, Local Weather and Forecast.
So now I'm paying $7.98 extra a month instead of the $3.99 for weather alone, but at least I have weather.
Anastasia is still clueless, and anyone who reads this now knows something that isn't in the XM Listener Service Representative manual – it seems that even though XM offers XM NavWeather as a standalone for $3.99 a month, you can’t get it unless you pay another $3.99 a month for XM NavTraffic.