I have tried to use the UIPrerenderedIcon/\"Icon already includes gloss and bevel\" on the Info.plist of my app and it worked perfectly on the Simulator, but not on the real
Muffle,
I had this issue and it resolved after I deleted the app off the device. Not sure why yours won't.
Right click on the info.plist file in XCode and Open-As a plain text file. Make sure your text file reads like this in the area for the pre-rendered icon:
UIPrerenderedIcon
I also had a strange occurence (in another app) where the info.plist file I THOUGHT I was using was set correctly. Then I opened up the file directly in the mac Finder window and it turns out XCode was using the wrong info.plist file. That's a long shot in your case, but wouldn't hurt to give it a try for a quick sanity check.
Hope that helps,
Rob