The following thread covers the topic pretty in-depth, but it sorta goes in a few different directions and can be confusing:
http://developer.anscamobile.com/forum/2010/07/06/iphone-4-problem
So I decided to throw up a quick 3-step tutorial on CoronaSDK.com for anyone who needs help getting their projects configured to use the retina display (while still preserving the low-res graphics for older displays):
–> http://coronasdk.com/2010/retina-display-setup-in-3-easy-steps/ [import]uid: 7849 topic_id: 2527 reply_id: 302527[/import]