Using calloc, the allocated space for the answer is set to zeros. The answer can't be more than 58 chars with the NULL terminator, so what gives?

without seeing you code, I'm gonna take a wild guess you're forgetting the NULL terminator

you have to return a dynamically allocated string

did you include the first test from the sample tests in your foreign environment? because one possibility is that you are trying to access the NULL array on CW which has no valid memory...