Looking at your other post about pcmcia, and now an X-display problem, I looked up the Latitude C840 and found out that this machine is probably pretty close to brand new. A lot of the problems you are having now come from the fact that the kernel RedHat 7.0 shipped with was 2.2.16, which is 2 years old. Knowing Dell's prediliction for Nvidia video cards, RH 7.0's support for your card is probably minimal at best.
RH 7.0 was also one of the buggiest distro releases ever.
The current RedHat release is 7.3, and is much less of a mess than 7.0. A lot of these problems will go away if you install a newer distro.