the given Key was not present in the dictionary


We have been using this web part for a while now and have just run into a major issue.
On one of our lists we needed to add a new field, and after doing so, we wanted to go into the "display settings" and update the columns. When we do this, we receive the following error message:
"The given key was not present in the dictionary. "
I have since figured out that if you change any field from required to not required or vise versa, you will recieve the error message. In order to fix it, you need to put the field back to the original form you had it in.
the whole issue with this is that if you need to change a field, the only way around it would be to create a new field, copy all the data from the old to the new field and then delete the old field. Not really ideal, especially when dealing with large lists.