Sorry. I havn"t Mac, but Garmin say about problems after update collars on Mac computers. May be some problems exist with Astro too.
But if you have to update 2.40 you need only copy gupdate.gcd (version 3.40) file in Garmin folder in Astro.
You can download itor this forum, rename to gupdate.gcd and copy.Code:Please Login or Register to see the links
No need to run webupdater or updater.