When we released the Flex 3 SDK (build 477), we injected some serious PopUpButton bugs that were not around in Flex 2.0.1. Somehow, these problems slipped through the cracks in our testing. 😦 The general problem was that the popup for a PopUpButton would not show up in various scenarios. Here are a sampling of the bugs:
Last month, we fixed the PopUpButton bugs that we were aware of. We have not released an official update of the Flex 3 SDK, yet. However, since we are opensource, you can grab these builds from our opensource website. You can find “stable builds” of Flex 3 (which include these bug fixes and others) at: http://opensource.adobe.com/wiki/display/flexsdk/Download+Flex+3PopupButton menu when combining
On the downloads page, you should see nightly builds along with “stable builds”. Stable builds have had more tests run on them, so, we expect their quality to be pretty high. You can find the PopUpButton fixes in any build after 2000. So, the stable builds 2113 and 2490 should have the fixes that you might be looking for. Good luck!