Looked into the ICS source code - It seems like for whatever reason the Package Manager can't get your package info - it could just be an eclipse/ADT bug where eclipse holds some kind of lock on the file, but whatever it is, it doesn't seem like something that you could cause with your code. I would suggest running a clean, uninstalling the app from the emulator/device, or if those don't work, you might try a fresh eclipse workspace.
Another thing that might be an issue is if you're using a Library project - try unlinking the two, cleaning, and then linking them back up again - but thats it for my bag o' tricks :)
UPDATE: yorkw gives a better explanation for why this occurs and its resolution here: RuntimeException: Unable to instantiate application