My Mac blackscreen's during Alliance Battles

Hey, i have downloaded the game from the GuildWars site through the client to my mac and to a separate pc running windows 7 ( to which this problem still occurs)

the game runs fine normally in missions and general running about.

The screen goes black, yet i can still make out my party, my chatbox and options button.

The Kurzick and Luxon scores are easily identified as well as some character name plates.

i can hear music and move around yet cannot see what is actually going on.

Im in the process of re-installing the game on the mac to see if it makes any difference.

.. on the Mac im running the game through a program called X11.


Thanks Pricey

Im pretty sure its your graphics card. I get the same thing on my laptop so i can only do big pvp games on my pc.
Same thing happens in ToA and random ra maps.