Hi scarmack,

Please try to use the .net 4.0 application pool.

There is a related thread that may benefit you:

http://social.technet.microsoft.com/Forums/sharepoint/en-US/8105110d-1913-49a5-b391-c3cc532d3faa/unrecognized-attribute-type?forum=sharepointgenerallegacy

On the other hand, your issue is about the sharepoint. I suggest that you should post it in the SharePoint Forum for efficient response.

Thanks

Best Regards