IIRC, DirectX 9 support in 6.2.0 was fairly limited. I wasn't able to use it until about a month ago in the nightly builds, and even now it only seems to work for me in a WinXP bottle.
Things are improving, though. Stefan Dosinger has been doing a fair bit of work on DirectX9 support, especially with regard to Guild Wars. I'm currently running the nightly from November 26th on my iMac. I'm using DX9 in windowed mode with the window resized almost to full screen and most of the graphics options pushed up to max and it looks gorgeous. Only a few minor issues remain (occasional missing textures, invisible mouse cursor after moving to a different area).
My suggestion? Run with the "-dx8" flag until the next release, or try using a recent nightly build in a WinXP bottle.