I'm not sure if this is a widespread problem or not...
Anyway, Planeshift worked fine on my black Macbook (with 2.0 Ghz processor, 1 GB RAM, and 64 MB VRAM).. But I sold the Macbook and just bought an aluminum iMac (with 2.0 Ghz processor, 1 GB RAM, and 128 MB VRAM).
Now, when I open up the Planeshift application... I get this:

Any ideas of what it could be?