Found the culprit: it's the configuration option "OpenOffice.org/Accessibility/Use automatic font color for screen display" in the Options dialog. I had probably checked this box when trying something else a while ago, and then forgot to change it back. Sorry for the nuisance.
** Changed in: openoffice.org (Ubuntu) Status: Needs Info => Rejected -- Text in Impress is always black https://launchpad.net/bugs/99208 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs