Since to ubuntu 10.04 upgrade move of my drop-down menus have been dark-on-dark text, which becomes readable (changed background) when selected. I don't know what's causing this but it's a problem on Ambience and Radiance both. Any hints?
This is probably a problem with the theme files, it is probably specifying dark text on the dark background. Try to change to another (light) theme and look if the dark text is there, and try to change back again.