I previously posted how I solved the problem of RadioButtonGroups inside repeaters, you can see that post here. Unfortunately, today, I discovered that radio button groups are a scam. You don't need them at all!? Why, you ask? If you just set the "groupName" property, they are automatically created.
<mx:Repeater id="someRepeater">
<mx:HBox>
<mx:RadioButton id="Yes" groupName="{someRepeater.currentIndex}"/>
<mx:RadioButton id="No" groupName="{someRepeater.currentIndex}"/>
<mx:RadioButton id="Maybe" groupName="{someRepeater.currentIndex}"/>
</mx:HBox>
</mx:Repeater>
If you ever need to access your RadioButtonGroup, you can just call a radio button by its id, and use the "group" property. I really hope this wasn't common knowledge that everyone but me knew.