When integrating Highslide with your WordPress blog there are numerous additions that need to be made outside of actually installing the plugin. First you need to make sure that you have the highslide.css file located in the /wp-content/plugins/highslide/ directory. After that you need to make sure that you add the code listed below to the footer.php file of your blogs theme.
'hs' is undefined
I finally figured out that I had accidently copied a file from a previous backup that was using a different domain. Anyhow it ended up being that the footer.php file I was using with my theme was pointing to HighSlide CSS definitions on a domain that no longer existed. So if you run into this type of error check the CSS you added to your footer.php file for Highslide to work.
In the code below you would change YOURSITE to the proper domain.