Video playback choppiness

Alright, ever since my computer was repaired I've been having a weird problem. I let a video on youtube buffer all the way, and when I start watching it, it's incredibly choppy (only in HD). My internet speed is fine (5Mbps),and I don't have any different software running than before. It also happens on Hulu, even when I don't let it buffer.

Things I've tried

Re-installing graphics card drivers (didn't work)
Clearing browser cache (nope)

If anyone has an idea of what it could be, I'd appreciate a reply.

 

doesnt hulu and youtube both run on flash?

try uninstalling and reinstalling flash, see what happens.

 

I would also recommend checking your graphics drivers, although it is unlikely due to this only happening in a certain instance, I would always try this. Just check your GPU manufacturer's website to see if any recent drivers are available to fix the issue.