Is the type of the DefIcon "Project" and the default tool Path/ProcessFile.rexx? And where can I find "ProcessFile.rexx"?
I've tried a DefIcon ENVARC:Sys/def_amigaguide.info with the default tool "Multiview" and that works at least for ghosted icons, but never tried an Arexx script yet. It's probably not a bug in icon.library, looks more like a problem in the AmigaOS and Arexx concept ?!