Invalid Json

All of a sudden all of our Editor tables stopped working. I get the invalid JSON message. I see an ajax response with the data we need but when I run it through lint is says:

Error: Parse error on line 1:
data[{ …}, { …}, {
^
Expecting 'STRING', 'NUMBER', 'NULL', 'TRUE', 'FALSE', '{', '[', got 'undefined'

Any help would be appreciated.
Janet