Have you tried to jail break your iphone 4 today. You might receive the following error message:
“File Received Was Invalid”
To fix this simply go into ‘setting’, click on the blue arrow next to the wi-fi connection you are connected to and then change the DNS settings but clicking onto to it. Once you click into DNS, delete the numbers that are already there and change them to 188.8.131.52. Exit out and this and then navigate to www.jailbreakme.com (Note, include the www) and try again and it should work!