Computer not booting.

I tried long and hard to get my computer to boot. I quit Minecraft, went to the saves, saw the computers folder and everything. I closed explorer, (or library,) and logged on. My computer had the GUI with the screen, but the CC computer screen was black. I am using CC 1.5.8 for MC 1.6.2, with a normal stone computer. I tried it in other worlds, nothing seems to work. EDIT: With advanced computers also.

Are you using other mods?

In your mods folder, do you have a CC folder, or a CC zip file?

Try reinstalling forge and computercraft, it usually solves that problem