Choppy Veetle playback on external monitor

[abta1]

I have a 2.4Ghz i5 MBP with 4Gb RAM and when I extend it to a 1680x1050 21" monitor via mini displayport VGA and play something through a webrowser via Veetle, the playback is very choppy whereas if I move the browser back to the main laptop screen its perfectly smooth.

What's the issue with this?

 

[simsaladimbamba]

Do you use the integrated GPU or the dedicated GPU?
gfxCardStatus will show you which you are running. If you run the integrated one (i), try the dedicated one (d).