It actually popped up before E3. If you remove the spaces from the stack name, you'll be able to save it.
Ahhh! Thank You man.
Okay, for those of you coming here with the same issue, this is how to fix it:
- Go to your stacks ( Go ahead and select the stack you want to edit )
- Click on "edit this stack"
- Scroll to the bottom of the page where the title of your stack is and edit it so that there are no spaces before, after or even in between the title
- Add the games you want to follow and click on "save changes"