I just switched to a 'dark' theme (Xfce-dusk), and bugzilla's form fields hate me. The text boxes and dropdown lists all have white text on white backgrounds. Boo. Brian is sad :-(. I've explicitly told Firefox to keep the 'old' color scheme as default (white text on black background, but allow sites to override), since many sites look weird otherwise. Other sites with form fields don't have this problem.
I've got the exact same problem. For me i solved it by using stylish extension to extend the style sheet. The problem is that in the style sheet the background color is set to white but the foreground color isn't. solution would be to add the following to the style sheet: input, select, textarea { color: #000 }
Any updates after the switch to bz3.2? I haven't changed input color AFAIK and there is also the dusk theme now. (Btw, added myself as QA contact for bugzilla bugs, so I'll be notified for css issues).
I'm not using a dark theme anymore; dunno.
We use the, slightly adapted, stock themes now, so closing the bug.