I have installed Red Hat Linux 6.1 on my PC at work and my PC at home.
At work the text in Gnome Terminal is invisible: I just see a grey background with the current position of the cursor a black rectangle and the command prompt and any text I type invisible.
When running xterm I see a white background and the command prompt and cursor position one long black rectangle.
At home everything is normal.
If in order to answer this question, you need any particulars on my hardware, I'll be happy to supply them.