Visio 2010/SharePoint 2010 Internal Error #3400 Action 1787 Check in file

Problem:

Visio would display the following error when someone tried to check in a Visio file into a SharePoint 2010 Document Library:

Internal Error: #3400

Action 1787: Check in file

First try closing and reopening the file. Next try restarting Visio.

Cause:

One of the fields in the document library had been set to required and as no data had been put into that field the file wasn’t able to be checked-in.

Resolution:

In this case we were able to set the field to optional.