Just a quick update an why I was getting this error and how we fixed it. By WE I mean my bestest buddy ol' pal Angela Knight. Will post a link to her blog as soon as she starts one!
What it was is a custom Contentype that was based off the OOB Event ContentType with a bunch of custom SiteColumns where the offending SiteColumn was of type lookup. Problem was the custom ContenType was deployed to the SiteCollection level however the look up list was only provisioned at the web level.
So how did Ange fix it?
She removed the offending SiteColumn, Created a Web level ContetType thats based off our custom ContentType that's provisioned after the look up list is. Thus we no longer get the error. See the juicy bits below.