Use diskcopy (in the utilities folder) and create a blank image file, sized appropriately for the application in question. Example, I created 30 meg blank disk image, using Mac HFS extended, and then just copied the 24.5 Meg Mozilla folder over to the mounted disk image. Mozilla runs fine now. Did the same thing for Quicken 2002, and the installer was perfectly happy writing to the HFS disk image.
Seems many of the app programmers, in their rush to get these apps to market, haven't really ported all the file I/O routines to the Darwin OS calls.
Well, this is a work around at the expense of some disk space. One nice benefit is I can copy my quicken data and programs from my OSX laptop to my OS9 desktop with one file image, and back.

