Hello,
I've built Maxima 5.20.0 rpms and tar.gz and posted them to the
SF file manager.
http://sourceforge.net/projects/maxima/files
I hope someone can build a Windows installer and post it.
Please try this release and report success or failure.
I'll make a general announcement when we get a stable 5.20.x release.
Note that the 5.20 branch was actually made on Dec 2 (or thereabouts).
best
Robert Dodier