Oli999 :
Don't agree with either of these answers.
What was said is correct. My five year old netbook with a single core Atom processor handles Youtube just fine until you get into HD streams. I've got an 8 year old laptop that uses a POS single core celeron chip that also handles Youtube just fine. My old desktop, using one of Intel's first dual core chips, runs Youtube just fine. My wife's old computer, which had 2GB of memory and a $45 CPU from 2005 ran Youtube just fine.
Any new laptop, even if it's using the worst CPU from the current generation, is more than powerful enough.
I bought a new low spec laptop recently and it can only just manage streaming at 240 on youtube and even then stalls sometimes as it can't keep up.
I simply do not believe that a
new laptop will do this. What model do you have, and where did you get it? My guess is when you say "new" you really mean used, and got something off eBay that looked like a good deal but wasn't.
You don't need a particularly high spec laptop for streaming video but it is slightly more demanding than the above answers imply.
No it isn't.
An absolute bottom of the range laptop won't do it.
If it's using a CPU made in the last two years it will.