If I remember my precision rules correctly, and its been years since I've needed to use them, 100 X .0022222etc equals 0.2222, since you don't know the precision of the number 100....it could be rounded from 100.1 or 99.9. Now 100.0 X 0.00222etc would give you 0.22222 Just because a computer gives you upteen decimal places doesn't mean that the answer has the correct precision.
You didn't indicate processor, operating system or software you were using when you got the error, so its hard to help you. But, did you remember to dimension both numbers as double? Try multiplication with both numbers having the same number of digits.