I'm using Flash MX 2004 on Mac OS X 10.3, but when I try to install FlashCom
Server MX 1.5 it says "cannot find an installed version of Flash MX -
installation cancelled", or words to that effect.

I've tried renaming the Flash folder and executable but to no avail - please
help.

Same problem.

Is anyone going to address this?

try this, seems to have worked for me :)

http://www.macromedia.com/support/flashcom/downloads_updaters.html

Note you can only install the authoring tools on OSX you need Linux or Windows
for the server ;)