The default setting for the "firewall" in RedHat is to deny telnet access. That is a wise position. Instead of using telnet to connect to your computer you should use SSH, as suggested, since it provides encryption and additional security.
If you need to connect from a Windows computer you can use PuTTy. It's a free SSH client for Windows. Get it here:
http://www.chiark.greenend.org.uk/~s.../download.html
Håkan