I really appreciate all the help here.
I cannot figure out what the problem is. It is slowly progressing to the older leaves. The spears still look fine, so for winter I will protect them with heat tape (photo). I'll wrap with burlap and then bind the existing leaves with a nylon ratchet strap. Basically, I'm giving up on the existing leaves and hoping the growth bud and spears survive winter. I figure the odds are under 50%, but I have to try.

<table style="width:auto;"><tr><td><a href=" http://picasaweb.google.com/lh/photo/k_TXicBmFeKc04rB8Q4Rjw?feat=embedwebsit e"><img src=" " height="640" width="383" /></a></td></tr><tr><td style="font-family:arial,sans-serif; font-size:11px; text-align:right">From <a href=" http://picasaweb.google.com/terdalfarm/November2010?feat=embedwebsit e">November 2010</a></td></tr></table>

Erik,
You might not want to wrap heat tape directly around soft tissue like the new spear. Lots of folks have told me that the tape burns everything it comes into contact with, except hard wood.

Steve,
thanks.
There are many types of pipe heating tape. This brand (MD) does not get hot to the touch, so I think it is OK to be in direct contact with plant tissue. I used it that way last year and it worked well. That might be because I used it under cover so perhaps it did not "need" to get very hot, but I don't think so as I also use it on exposed PVC water pipes in my barn and it never feels hot to the touch yet keeps pipes from freezing even in very cold weather.
I guess basically I am treating a palm spear as a water pipe. 😯
--Erik