WPMU Issue #2 (Possible OT): Template and Plugin Upload Error

This may be a long shot but I figure I'd give it a shot before starting from scratch with a new theme.
It's unclear as to what templates will run under WPMU so my initial assumption is that if they run under WordPress then they're likely to run under WPMU. Case in point where I have a template I customized called Freshy2, which is located here:


I've customized the theme on my test WIMP server and all seems fine, as seen by these two samples:


This particular theme comes with a separate plugin which controls the customization settings. After uploading the theme and plugin to my live WPMU site hosted at GoDaddy I get the following error when activating the "customization" plugin:

Fatal error: Call to undefined function wp_get_current_user() in /home/content/k/g/m/haiti/html/wp-includes/capabilities.php on line 969

I've posted a message to the author's website and the WordPress forums but no response. So I figured I try here to see if I can get some direction on troubleshooting the error.

Any responses appreciated.