string? the data types involved are int and int array, and there's nothing about "-" in the problem description, are you posting on the right problem?
is that the full error message or are you just giving a small part of it out of context? what language is it? better yet, how can others get the same error message? if you print out input as well as your own input, does your program appear to do what it should?

@ Dr_Phill:

"If both i%3 and i%5 == 0, then the statement becomes 0 + 0 which is simply 0, the same as False."
you mean in that case they will both be True (which gives us a 1) which results in a "FizzBuzz". The rest is good :)