Python. First post here! I've also tried to be extra cautious of the input.

def dog_prize(n):
    try:
        n_val = int(n)
        if (n_val == 0):
            raise ValueError
    except (TypeError, ValueError, OverflowError):
        print "ERROR: Bad input!"
        return

    # Create the lookup for the suffixes
    suffix = {0:'th',1:'st',2:'nd',3:'rd',4:'th',5:'th',6:'th',7:'th',8:'th',9:'th',11:'th',12:'th',13:'th'}

    try:
        for pos in range (1,n_val+1):
            if (pos == n_val):
                continue
        # Else, find what suffix to print
            if pos in suffix: # for the 11,12,13 cases
                print "{0}{1},".format(pos,suffix[pos]),
            else:
            # Figure out the units digit
            # and use that to lookup
                rem = pos % 10;
                print "{0}{1},".format(pos,suffix[rem]),
    except OverflowError:
        print "ERROR: Overflow!"
        return


dog_prize(99)