I recently set up a HTML5 video system with flash video fallback, for those crazy people with old browsers. VideoJS.com is a great site for explaining how to do this. Use this with the site with the info here for a great solution.
Anyway, the flash fall back using Flowplayer commercial was giving me a bunch of issues on IE7 & IE8. One was there was an error that was being logged in the console about 'SetReturnValue' not being defined. Turns out, the <object> tag must have an ID. The example code I copied from VideoJs's front page didn't have this. So, make sure you have a unique id set.
The other issue had to do with Flowplayer's branding removal (with a commercial license). Turns out, the registered domain name is not for the domain the video is being played on, but the domain the swf file is loaded from. I had the swf files on a CDN and the branding was not removed. Just had to move it back to the main site and all was good.