I can't answer the complete question, but I might be able to point you in the right direction:
The message is from JMP's scripting language, JSL. A "map" is an associative array that can be indexed with character strings (keys), unlike a matrix that can only be indexed with integers. The "key" is the index to the associative array, and the message means no value has been stored using that key. If you have the JSL, the variable name you are looking for is "key" (based on the message you got). Using show(key); in the JSL might tell you what's wrong.
Guessing in the dark: the key that isn't found appears in your data incorrectly.