My copy of Rapidweaver 7.5.1 does not register it has just added new Stacks. For example if I attempt to reload the same stacks again, previously I would show that those stacks were already loaded. Not so now.
Just today, when Stacks 3.5.5 (#build 4120) update just came out, I added the update, but RW keeps nagging me to add it again and again. What the @#$@#
I’ve heard of interesting situations like this when the RapidWeaver add-on updater gets a bit confused about what is currently installed.
I’ve not actually seen this happen in person – so I’m not sure what the specific “confusion” is – but it is definitely something about the add-on’s folder.
I would open up the add-ons folder and have a look. Use Cmd-Opt-7 with RW open to make sure you’re getting the right one – don’t presume you know the right one – there are too many possible locations.
Once you have the folder open, just check out what’s in there. If you see any obvious problems (duplicates, things named strangely, etc) take care of those things.
If you see nothing amiss, then I’d recommend downloading Stacks directly from http://yourhead.com/stacks and adding it directly.