I'm posting this again because I didn't get a response to my original post and this is much worse than my original title indicated. I'm hoping this new title will get attention as this is CRITICAL - not just because it destroyed our site but because it could happen to others as well. So the sooner this gets your attention the better for everyone.

Please see my original post here for all the information and then you can delete this. www.artio.net/support-forums/joomsef/cus...f-4/error-on-install

Our site is completely corrupted as a result of installing your extension. Please help ASAP. Thank you.

We found a solution and I'm posting it here for the benefit of all and for the developers so that they can fix their bug.

The problem is joomla global SEF settings are enabled by default in joomsef when you install. We disabled everything from configuration.php file sef=0, debug=maximum and now everything is fine.