While your box is online, try a "dmesg | more", is your cdrom recognized?
When you installed, did you make multiple file systems or just "/" and "swap"?
Since you did a few installs, did you select the "bad block" check option?
Definetly review fstab, logs, dmesg, /var/log/ , etc...to try and identify the cause?
If you reinstall (again), try multiple File systems w/ext2 (maybe most stable?)...this way you can narrow your issues down to a single FS (if bad block)?
You might want to upgrade your packages, I use "apt-get dist upgrade".
Review any errata's RH may have on their support site.
Have you used this hardware for linux before?
You might want to search the net for any possible compatibility issues associated with your hardware....