Flex 4 Scroller sometimes doesn't show
Ok so I have a simple unskinned Scroller component , the problem I'm having is that at aparently random times the vertical scrollbar dissapears. 
I can still scroll the content with my mouse wheel but you can understand how that's just not enough for a quality product.

here's my code

    <s:Scroller id="scroller" width="100%" height="150" horizontalScrollPolicy="off" verticalScrollPolicy="on">
		<s:DataGroup
			dataProvider			= "{_myDataSource}"
			width				  	= "100%"

			clipAndEnableScrolling	= "true"
			itemRenderer			= "MyItemRenderer">	
			<s:layout>
				<s:VerticalLayout
					useVirtualLayout	= "true"
					rowHeight			= "30"
					gap					= "10" 
					horizontalAlign		= "left" 
					paddingRight		= "10"
					verticalAlign		= "top"/>
			</s:layout>
		</s:DataGroup>
	</s:Scroller>

Is it a flex bug? 
As I've said it seems to happen randomly. 
The only thing I do know is that it only triggers when and if the data source array gets changed. For instance in a chat window where messages keep comming in.
This occurred for me in multiple places so I'm thinking it's not the ItemRenderer that's causing the problem.
Flex 4 Scroller sometimes doesn't show
===

Ok so I have a simple unskinned Scroller component , the problem I'm having is that at aparently random times the vertical scrollbar dissapears. 
I can still scroll the content with my mouse wheel but you can understand how that's just not enough for a quality product.

here's my code

    <s:Scroller id="scroller" width="100%" height="150" horizontalScrollPolicy="off" verticalScrollPolicy="on">
		<s:DataGroup
			dataProvider			= "{_myDataSource}"
			width				  	= "100%"

			clipAndEnableScrolling	= "true"
			itemRenderer			= "MyItemRenderer">	
			<s:layout>
				<s:VerticalLayout
					useVirtualLayout	= "true"
					rowHeight			= "30"
					gap					= "10" 
					horizontalAlign		= "left" 
					paddingRight		= "10"
					verticalAlign		= "top"/>
			</s:layout>
		</s:DataGroup>
	</s:Scroller>

Is it a flex bug? 
As I've said it seems to happen randomly. 
The only thing I do know is that it only triggers when and if the data source array gets changed. For instance in a chat window where messages keep comming in.
This occurred for me in multiple places so I'm thinking it's not the ItemRenderer that's causing the problem.