Can you post the %post section of your kickstart file. This will help with diagnosis.
You can also try adding
To the %post line like so
Anything that is echoed after that line should then be logged in the file /root/my-post-log on the new install (you can look at this file using something like knoppix or the rescue mode of the install disk if the OS won't boot for you after the freezing in the post steps.
Putting a line such as
echo "Started Post section of kickstart"
straight after %post should cause output to be put into the log file.