Did quick check and got Silverlight to run on Firefox, IE, Opera and Safari.

I am accessing through the NBC site, clicking the date of event, then event.

It should give you the option to watch "rewind" or live. Watched the 49er races last night live. Appears that they are doing only one 'Featured " fleet per day - but last night was wire to wire coverage of 3 49er races was much better than all past US sailing olympic coverage combined.

FYI if you are pumping the feed through to a plasma TV and have Vista Home Premium or Ultimate you can use Media Center to get the image full screen with additional picture in picture.