Another long shot.... once you reach the login screen, try unplugging the keyboard and plugging it back in. If that doesn't work and it's a USB keyboard, try plugging it into a different USB port. If you've only been trying PS/2 keyboards, and you have a usb keyboard to try then give it a try to see if it works.
My only other idea is to ensure that your install CD is 100%.
To see if the CD is 100% then you would boot from cd and at the 'boot:' prompt you would type 'linux' without the quotes. This will load the text user interface installer (TUI installer) at which point you'll choose: Start, Install, Check, and then using the spacebar put an 'X' next to each option and then hit Enter. This will start the process of ensuring that all installable data on the disc is correct. The process will take many minutes and will provide a message indicating if there are any problems with the disc. If no problems are found then the installer will start walking you through a new install starting with choosing a 'Swap Partition'. If you do not want to reinstall using the TUI installer then just use the right arrow to choose 'Cancel', after which you can 'Exit' the installation.
