HAVING Clause problem

[BruceG]

I've got a puzzler here. I have two MAS tables connected to Access 2000 thru the ODBC driver. In the SQL query window, I have the following:

SELECT CustomerNumber, COUNT(*)
FROM AR4_OpenInvoice
GROUP BY CustomerNumber
HAVING COUNT(*) > 10

The problem? The query runs but produces no records.
I take the HAVING clause off, and it runs - I see the CustomerNumber, along with the counts (many of which are > 10)!

Is there some kind of bug in the driver or some issue where the HAVING clause does not work as expected? I tried a similar query using the Northwind sample database and it worked fine. (I did the following):
SELECT OrderID, COUNT(*)
FROM [Order Details]
GROUP BY OrderID
HAVING COUNT(*) > 2

Any ideas? TIA.