I have a little more information after messing around (still no solution yet)
Again, I am running a Multi-Site version of WordPress 3.0.1
I activated the plugin that creates the table logged in as the Super Admin - however I activated it while being in the "backend" of "sub-site" #3.
The table is created for that account ONLY.
Screenshot from PHPMyAdmin: http://grab.by/5IRt
All other accounts show this error in their backend:
Fatal error: Call to undefined function wp_get_current_user() in /home/muswap/public_html/wp-includes/capabilities.php on line 1059
So the plugin appears to work for only the account that is activating the plugin. The rest of the accounts show an error.
Any ideas why?