Flex 2 History Manager gotcha on Internet Explorer
If you are creating a custom wrapper for a Flex 2 project that uses the History Manager, make sure that you set the width of the IFrame that houses history.htm to at least 22 pixels. Otherwise, it works on FireFox but doesn't work in Internet Explorer. I was pulling out hair today trying to figure out why my example wasn't working in IE until I stumbled across this.
If you use the default wrapper created by Flex Builder, the IFrame's width is set to 22 pixels by default.