It seems that this problem can be "worked around" by changing the anti-alias settings.
For me, setting font anti-aliasing from "None" to "argb" in the 'gnome-tweak-tool' or the KDE settings center unbroke the unreadable fonts in openoffice. However, this seems to be system dependent. It has been reported that on other systems, any of these three settings do.
It remains unclear to me what the actual underlying problem is.
-- regards, Reinhard