If you're using Internet Explorer 7 (IE7) or an earlier version, try upgrading to IE 8. It worked for me...so far, so good, that is!
Forget using IE8 IMHO. I'd updated from IE7 to IE8 and it worked for a little while but then my whole computer started having problems "hanging" with the "new & improved" internet explorer so I went back to IE7.
I went to plan B and downloaded Google Chrome and it works but it's a real striiped down browser but beats the heck out of IE8 but I still have problems with the streams not connecting at times so it seems it really doesn't matter what browser is used!
Recently IE7's been working fine tho I've had the same problems others have mentioned... occassionaly nothing is streaming or streams working for a little bit then loosing signal, only stills are available, or vehicle icons show to be streaming but I'm unable to connect.
I really feel it's a bug in the system as I am able to watch streams on other chasers websites without the connection problems I have on this site. But I prefer this website because of all of the great folks here.
So all I can suggest is to have patience, enjoy the streams when you can get them, and be thankful for what we do get!