I had this issue to. The solution is a bit odd but it works. You'll have to follow the following steps:
1. Add the Insanelyi repo (repo.insanelyi.com)
2. Install iRetiner from there. The reason it must be installed from insanely is because insanely doesn't require ImageMagick, instead it uses EricaUtilities.
I tried this and it worked. This was the way installed it the first time I got but I forgot about for a long time, then I found this video>> [ame=http://www.youtube.com/watch?v=n8IZzNZMCTI]YouTube - Make All App Icons Retina Compatable!for iPhone 4 and iPod Touch 4G(Thanks to iPodTouchHelping)[/ame].