I had inherited a Sitecore instance from a previous vendor and one of the main questions the client had for me was about items in their workbox.  This specific Sitecore instance had over 29 different languages, over 35 different microsites and content editors from around the world.  When I opened the workbox, I found a whole list of items, all of them claiming 'No Changes have been made'.  When I tried to submit any of them, I would get a generic Sitecore error and the log files weren't helping me narrow it down.  I had assumed with all the moving parts, something catastrophic had happened.  Turns out the issue was rather simple.

[Sreenshot of over 200 items in this limbo state]

I opened the item and viewed the Standard fields.  Turns out the state was filled but not the workflow to which it belonged.

Once I had correctly assigned the items, the workflow worked as intended and I could clear the items for the client.  Be sure to check your workflows.