Hey Team
I just found out that your "panel_preupgrade_checker.php" got a bug.
It failed for my server at check #24 and stopped there:
[2012-07-06 03:20:56][INFO] ==> STEP 24: Checking the availability of Plesk Panel TCP ports...
[2012-07-06 03:20:56][FATAL_ERROR] Unable to get IP address...