I have tried to install redhat 6.1 three times, twice using the entire downloadable redhat i386 directory located on ftp mirror sites, the third using the downloadable ISO image (mounted the ISO image under linux and copied it to my DOS hard drive to ensure that all proper files were present). All three times, I have experienced a dialog with the title "Exception Occurred" whose main body contains the following message (at the bottom): "TypeError: unsubscriptable object" in reference to line 50 of "comps.py" ...this is after configuring the installation and after the program begins to read packages from the install directory.
The most common cause of this error message that you are getting is that there is a file in the RedHat/RPMS directory which is not actually a .rpm file. Change into that directory and run "ls | grep -v rpm" If you get a list of any files (which I am expecting that you will) delete them and you should be able to continue with the installation. Please reopen this bug if you are still having problems after following these directions.