After testing with Firefox 4.0, Nightly 6, Firefox 3.6, Google Chrome, I found out that Firefox 3.6 is the one for this Win8 build, all others had crashed. I am using Firefox 3.6 now.
Yes, I am getting sounds from both IE9 and Firefox 3.6. First, I need to install my sound card driver in win xp compatibility mode(I have sound blaster live card), then install the newest adobe flash player for both IE9 and Firefox 3.6.
9600 GT + Forceware 270.61 = IE9 Slow!!! in another PC without VGA driver compatible (S3 Unichrome) works normal (not too fast, but not lag)
I think all these win8m1 problems depend on the PC hardware, especially the video and audio cards. I had no problem on my 2 laptops with IE9 Firefox 4.0, but had problem on an older desktop with Firefox 4.0 (Ati HD3450 card).