XPCOM issue in MacOSX

(cross posting to the macosx and xpcom groups, not sure where this really 
needs to be)

I have an xpcom object installed with my .xpi, and it has worked so  far on 
windows and linux.  In bringing it to the mac, I've had mixed results.

When I load firefox (1.0.2 release binary) by clicking on the Dock icon, my 
xpcom object fails to load, nsIJSCID.createInstance returns 
NS_ERROR_XPC_CL_RETURNED_FAILURE.  If I run firefox directly from a shell 
window, with ./firefox or ./firefox-bin, everything runs perfectly.  I can 
also get the failure buy running open Firefox.app from the shell, 
simiulating the dock launch.

What is different between open and running firefox directly I am missing?

Thanks,
Mike