What operating system are you using? Could you put the link to the Kuler panel you downloaded?
I downloaded from the blog at www.pixelfumes.com
I just went into FW and checked the version >1.3
Model Name: iMac
Model Identifier: iMac7,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2.4 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache: 4 MB
Memory: 2 GB
Bus Speed: 800 MHz
Boot ROM Version: IM71.007A.B01
SMC Version (system): 1.21f4
Okay...this post: http://blog.pixelfumes.com/?p=228 ( I commented on that.)
Well, I'm not on a Mac at all, so I don't know what your particular installation problem might be. With Vista, you need to run the extension manager as an administrator, or the extension won't install in a way that can be used. Does the Mac OS have that kind of distinction? If so, you might try running the extension manager with elevated rights.
Have you contacted the creator of the extension?