If you dump the form scope, are those numbers presented as a list or an array?
Do you have the thissameFormFieldsAsArray setting set to true in Application.cfc?
Recommend you put a try/catch around the erroring code, and dump out all the contributing variables to determine which variables don't have the values you expect.
Also: is your CF10 server fully patched to 10.0.11?
--
Adam
