When you say you're "seeing a lot of videos...", does that mean some will play and some won't?
If so, please give me a small list of ones that will and ones that won't play, and I'll look into what kinds of qualities set them apart that might be causing the problem for you.
If absolutely none of the videos are playing in one browser while all of them are in another, then it's likely to either be a problem related to your Flash installation, or perhaps the way certain browsers interpret the Javascript that assists in rendering the video. My first guess is Javascript, since you say you're seeing an empty play/stop bar, which means that Flash is likely loaded and working fine.
I'll check Google Chrome and IE7 under Windows 7 and let you know what I find.
Regards,
Jonathan