Installing msttcorefonts did the trick. All new documents compose nicely regardless of font.

However, for some reason all of my *previously* archived documents still open as garbage. I'll be working on a fix for that today. Meanwhile, each document can be restored manually if you open in Abiword,"selelct all," and then click on the"normal" setting in the drop-down style menu.

Maybe someone else knows a more efficient workaround?

Just a brief follow-up about Abiword opening previously composed documents.

It looks as though RTF files composed by some other word processors (like Ted) open as garbage in the new Abiword 2.6.4. Again, they can be manually cleaned up (as explained above). There seems little problem if one works (and has worked) exclusively in Abiword. I don't know how much anyone else is being affected by this...