You should try deleting the cache file to see if this helps to resolve the js error you are receiving, here are the steps for this:
common_installation_issues.pdf
If this does not resolve the issue for you there might be a corruption of your configuration folder. If this is the case follow the directions here to overcome the issue:
showpost.php?p=12293&postcount=2
If you try these things and the issue persists please let us know.