This is a bug. As a workaround, set List property useVirtualLayout=false
yeah i figured.
got another potential critter for you. you prefer i submit a bug report or does this forum suffice?
I'll submit a bug.
Personally I think it is easier to just file the bug in the bug base (http://bugs.adobe.com/flex) -- and that way you know it won't get missed in all the forum traffic. If you want to post a note in the forums saying "I just filed bug SDK-12345, does anybody have a workaround?" or something like that, it may help expedite the bug process.
Oh, and attaching simple test cases to your bug reports helps us (Adobe) out a lot.
This worked in beta1 and not in beta2 because the default value of List.useVirtualLayout was changed from false to true.
As Ella mentioned you can get around this bug by setting useVirtualLayout="false" on the List, but that will mean that every item gets rendered (even those not in view). This is a problem when you have a List with hundreds or thousands of items. If you need to use a virtual layout there is another workaround available: set the minHeight of the renderer to a non-zero value.
Attached is a ZIP with sample files demonstrating the workaround.
You will notice in the first sample that scrolling is a little choppy. You can correct for that by defining the typicalItem to be the largest item and providing a more reasonable minHeight in the renderer. This flickering is a consequence of virtual layouts with items of varying sizes (see http://opensource.adobe.com/wiki/display/flexsdk/Spark+Virtualization for more information on virtual layouts).