I'd like to ask you for a little more information about this problem, so that we can look into it, if that's OK with you.

What kind of iOS device are you playing VF2 on (iPod touch, iPhone, iPad), and about how long have you had the device?

Has this problem been happening since you installed the game, or did it work properly at first?

If you perform the following procedure, does the game start working properly again?

1) Hold the Sleep/Wake button on your device until the red slider appears, then slide to power off.
2) After the device has powered off, hold the Sleep/Wake button again until the Apple logo appears
3) Once the device is completely powered on, launch the game again and see if the game operates properly