Cross Santiago.6327

How about unplugging one of the cards?Don't know if that will help if it's a power issue.

actually it's probably best if you dual boot with windows 7 using bootcamp, because gw2 runs faster on it.

If your Mac uses two graphics card(one onboard, the other external) make sure that the external is the default one. The external or discrete is usually the more powerful card.If it's nvidia, you should be able to change this with the nvidia software preference, if it's others like radeon I don't know.