Will,
The general server error reported by the FP Write.vi is because you are not writing enough values to the tag item that you created in FP Create tag.vi. For example, if you are writing to the "All" tag, then you will need to write to all 8 channels of the FP-AO-200. In conclusion, the array that the FP Write.vi uses will need 8 values, no more, no less.
JohnM