Unable to create site based on template - Failed to apply template "STS#0" to web at URL error Non-supported field type change. The field cannot be changed to the new type.

We had a custom site template in Sharepoint 2007.  Since 2007 site templates could not be upgraded to 2010, we used the following process:

- in Sharepoint 2007 create a temp site based on that 2007 site template

- perform upgrade of the whole system to 2010

- Now export that upgraded temp site in 2010 as a template

Exporting as a site template worked fine.  However, when I try to create a new site based on that template I get:

"Failed to apply template "STS#0" to web at URL <url> error Non-supported field type change.  The field cannot be changed to the new type. "

First, is there any way to find out which field it is complaining about?  Would it really be so hard for Microsoft to actually display some more useful error messages such as "non-supported field type: <field name>"?  (Sorry, this is not a question, just an observation)

Second, we had some custom site columns in that template so maybe it's complaining about those?  However, I did verify that all of these custom site columns use the site column types that are still supported in 2010: multiple lines of text, Yes/no, Lookup, Number, Choice, Person or Group, Single line of text.

Is there any way to fix this other than re-creating the site in 2010?

thanks,