Error while changing the default application with which we open a file

Recently I've tried to change the default application with which a file is opened, by doing the following: 1. Right click on the file 2. Get info 3. In "Open with", change to the application you want your file to be opened with. 4. Click on the "Change All" button which is found under the "Open with" label in the last step, i.e. when I click on "Change All", I receive the following message: then if I look at the default application that opens this file, it's really the application I've just chosen, but when I click on the file to open it, I've the following error message: Yes, I was trying to open a Makefile for a C program. Any ideas of why this is happening and how to solve it?