Resolved: An Unknown Error Occurred (0xE8008001) on iPhone

The Application “Sygic Australia & New Zealand” was not installed on the iPhone “My iPhone” because an unknown error occurred (0xE8008001).
I got this error message when I was trying to install Sygic for my iPhone via iTunes.
Have you ever got similar error message while installing apps to your iPhone?
Q: Why did you get this error?
A: It happened because you have not installed AppSync on your iPhone.
Q: But I have jailbroken my iPhone?
A: Just jailbreak the iPhone is not enough. After that, you must install AppSync 3.0/3.1 (depend on OS/firmware version). Hence, you can install any cracked apps for your iPhone.