nopain180 is right on the money. Create the new table column in mySQL to tackle the fieldset error. The image uploader is the prob.
I also ran around in circles for a while on a test site, because selecting the display page from their little drop down wouldn't work (blank screen). Turns out permalinks have to be pretty to get the content to show up on the page (just a little tip for the testers).
There is also a rogue apostrophe in inventory.php on line 177.
User experience on the plugin site is... well, it's bad. It gave me a minor anxiety attack.