fjw

On mac the problem is the path format.
[opendialog] gives this format: harddrive:path/to/file.als
[max.launchbrowser] needs /Volumes/harddrive/path/to/file.als

If you like I could send you my playlist version of your patch which is working on Mac at the moment

This patch works fine if you manually enter the path to the .als file in the .js file. I'll modify this patch to work with a playlist. Does the author of this patch have any problem with distribution of an adjusted patch on maxforlive.com? Or do you want to post it yourself once it's done?

This is the error Max produces:
Max could not launch URL. err = -43