Per barryhunter here, here's what the answer is: I asked,

> My version 4 beta problem is that my URLs no longer work. My syntax has been:
>
> http://maps.google.com/maps?q=48.890706,2.363186&output=kml

-- now any such URL has to read, instead, in GE3 and GE4,

http://maps.google.com/maps?q=@48.890706,2.363186&output=kml

I hope they don't change it again...