I would imagine that the problem is, as the configure script says, that libXext is missing. Look for an RPM for RedHat or Mandrake. They are probably easy to find if you paste the name of the missing file into a google search. It's also possible that the library simply isn't being found by your operating system, although this is a bit less likely. If you KNOW that you have LibXext, you may want to man ldconfig.