You're probably getting tired of hearing this by now, since it's at least the third time I've reported it, but there is still no support for serial Kensington Thinking Mice. They really do exist, I swear! At any rate, whether doing an X-based install or text-mode install, there's no option to select serial Thinking Mice. There's one for PS/2 Thinking Mice, but obviously that doesn't work if your mouse is actually on a serial port.
This issue has been assigned to a developer for further action.
As of RH 6.2, this *still* isn't fixed.
Kensington Thinking Mice have been added to the mouse list ... you should see it in the next release ... thanks for your report!