All,
In one of my forms I often get the error below when I want to change a label. Same on TST and ACC environment. (SP2013, NW2013 latest release, NF2013 latest release)
Anyone an idea about the cause?
Thanks,
Glenda
Are you using custom scripts?
Have you at that momento any script error?
Try debugging and seeing the line of code with error.
I too just got this same error when attempting to change the description of a label. My workaround was to delete the label and recreate a new one.
+3We just had this same error reported by one of our form developers, She was just trying to edit a label in the Nintex form as well. We are on SP2013, NF2013 latest release as well. Did anyone ever provide a solution to this problem?
Thanks.
+2- Nintex Partner
THANK YOU:
This just happened to me trying to resize much of my label text during a form makeover session. Recreating the problematic label is the best solution! 
+5Not sure why the error occurs. However if you disconnect the label from the control so it's not associated (Associated control = Not connected), you'll then be able to edit and update your label without recreating it.
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