Items can't be duplicated with 8-char random string ID based data types

[wwwysocki]

Repro:

1. Create a global data type or page data folder (use defaults).
2. For the GUID, select 8-char Random String
3. Add at least 1 field, e.g. String (use defauls)
4. (For page data folder type, add it to a page)
5. Add an item of this type.
6. Duplicate the item

Expected:

Duplicated OK

Actual:

A server error with an exception

System.ArgumentException: datasetParameter name: Key violation error. A data element with the same dataId is already added. Type: Test.Bzbz
at Composite.Plugins.Data.DataProviders.XmlDataProvider.XmlDataProvider.AddNew[T](IEnumerable`1 dataset)

Note:

Data types with IDs based on GUIDs or 4-char Random Strings seem to be working OK