Can't add same item to DataGrid twice, even if I delete the item before adding it again

If I add an item to my DataGrid, then delete it, then try to add it again, I get this error:

assertion failed in ItemFileWriteStore

Any idea why this could be happe开发者_如何学Pythonning?

I'm using Dojo 1.5.

if you try to add an item that was removed from a store without calling save() on the store you'll get this error. Stores have an 'un-delete' feature. check the ItemFileWriteStore API for isDirty() and save().

no two items in the store can have the same identifier at any point of time..