I always have massive problems watching YouTube in Chrome, but I assume it's because my computer is very very old, very very shite and doesn't have enough memory.
It is related to Adobe Flash Player though - whenever I open two or three tabs with some kind of embedded video content (i.e. advertising), it all gets slower than an extraordinarily slow thing and eventually I get a message saying Flash Player has crashed.
Sometimes I disable Flash Player, but then I get pissed off because I can't even try to watch anything on YouTube.