Colin,

One more question. Can you attempt the float sum again, but this time specify the ordering of the rows? I ask because an unconfirmed source (wikipedia) seems to indicate that addition is NOT associative.

Thus (a + b) + c = a + (b + c) is not always true for floating point numbers, if this article is true.

select ID,[some float column] from [your table]

order by ID

Compute sum([some float column])