Thanks Alex specifying a rowHeight fixed the problem. However there's still an interesting/odd thing in this case which I forgot to mention in my post. The setter itself executes twice for every row in the list, and this also seems to be a default behaviour. To be more specific if the data provider recieves from the model: "one", "two", "three", "four" , the data setter trace outputs:
one two three four one two three four Cheers. PS. @Amy I have read the post on your blog, and to some extent you are right however in my case i was working with a repeater as a renderer before and it proved to be a killing performance issue. The repeater compenent created a new instance every time the model got updated. Considering the fact that I got 4 rows in the list and I was pooling data every 3 seconds that means at least 20 new object per minute. You can use the caching ootion of the repeater but still when profiling the appication the memory usage kept growing ang growing and never stop growing. When switched to List, the memory leak was not an issue anymore, but instead I got this 2 new issues one already fixed by Alex and the other one mentioned above. To conclude, event with the extra object created by the list it is still a better choice for me than the repeater.