Thanks answering that fast. 

Yes I think thats the problem too. We use a Generic List. We have a datacontract class containing child classes connected as Generic Lists.
We pass these as a contract over via WCF to the client where we bind them direct to the datasource.

Have looked at UltraDataSource but haven't found any nice way moving the data from the List to the DataSource. Is there any? Would it solve my problem?
The winDataSource could that be used instead with the same features? or do I miss some?

/Leif 

There's no automatic way to copy a list into an UltraDataSource, although writing code to do this would not be terribly difficult.

Maybe instead of List you should use BindingList.

Whats the best way to bind List<> to Ultragrid , given that i have to add new rows.. I tried Rows.Band.AddNew();  but it gives same error ..

List<T> cannot support adding new rows. Using BindingList<T> instead.

I'm trying to add rows to the infragistic ultragrid but I get an error saying.

 Unable to add row:
 Unable to add a new row. Underlying DataSource does not support adding new rows

I am using List