Youtube has gone crap. A % of the clips refuse to even load in Opera, it's not Opera as most of them work fine. I am always having issues with buffering, so slow it's stupid. Don't go off speed test sites, they are just as bad. I just tried one and it took seven different servers just to hit anything near 10Mbit (I am on 20Mbit)
Try this.
http://stage6.divx.com/videos?order=...&cid=DP0000007
This is one of the fastest sites I have seen. The Alex Gaudino - Destination music video buffered 120Mb or so in about 40secs. It topped out at 1.8Mb/s.
So I know the connection is fine.