Error when adding a reference to a WebService

[Martin Lee]

The following error message appears when attempting to add a refrence to a
WebService:

"You must implement the Add(System.Object) method on
Core.Service.DataSets.UserDataSet+UserDataTable because it inherits from
IEnumerable."

Other WebServices that use similar Strongly Typed Datasets do not cause this
problem. Does anybody have any ideas?

Thanks,

Martin