Clearing a Text Area field via the API.

I'm trying to clear a Text Area field on an object and save the change but Update() isn't actually updating the object in salesforce (though it runs without error). Here's basically what I'm doing:

sfObject.Field = "";

sfObjects.Add(sfObject);

salesForce.Update(sfObjects);

I know my code works properly since it does update SalesForce when I change the "" above to "Test". I've also tried setting the value to null to no affect. Do I need to set it to a space, set another property or call some other method?

Thanks,

E.J. Wilburn