Velasquez Julio No longer there

After our last upgrade one of our web forms that has been working flawlessly started generating the error: Error: The given key was not present in the dictionary. 
Has anyone seen this error?
It would be nice for DW to have a site to lookup error messages.

Gracias much..

Julio
Pittsburgh..

I have a web form where I will like to auto-populate the city field based on zip code.. has anyone done this?