I am having HTC Desire from past couple of weeks. Well we know that Angry Birds Rio was released recently. I have tried to install the same on the phone of mine and I have noticed that it was resulting into the error message. The error message can be written as Installation error Unkwnown reason -18 Let me know whether there is an issue with the game itself or with the phone of mine. let me know if you are having specific solution to fix the matter of mine.