A bit late, but apparently due to some patent issues, MS launched an update on April 11 which breaks Flash object interactivity in IE: you have to click the object before it will do your lovely mouseover type stuff. Well done Eolas, you’ve broken a large segment of Internet. This is yet another example of the ridiculousness of the US patent system and another reason to fight it here in Europe.
The link contains a discussion on the subject and fixes for developers.