What should I do if my app crashes on startup? (Part 2)
Q: What should I do if my app crashes on startup? (Part 2)
A: Here are some more solutions that you can try to fix the problem.
Perform a hard reboot of your iPhone, i.e turn your iPhone off completely, by pressing and holding the Sleep/Wake button (on top ) for a few seconds then slide the red slider. Turn it back on by holding the Sleep/Wake button until the Apple logo appears. This can clear potentially problematic data, preventing some type of crashes.
Delete the iPhone Application
If the above solution does not help, try deleting the application from your iPhone and then re-sync it back to your iPhone.
To delete an application from your iPhone, simply press and hold on the application icon on your iPhone's home screen until it begins to wiggle along with other application icons (just as you would to rearrange them). A small black circle with an "x" on it should appear on the top-left corner of the icon. Tap on the "x" of the iPhone app that is giving you trouble to uninstall it.
When thats done, sync your iPhone with iTunes which should result in the application you just deleted to get synced to your iPhone again.
Few iPhone users have observed that re-downloading the deleted application directly from iPhone's App Store (rather than using iTunes on your computer) also helps in resolving the crashing problem.
If deleting the application or full reboot does not resolve the crashing issue, try performing a restore of your iPhone. Connect it to your Mac or PC and, in iTunes, click the Restore button under the Summary tab. Please do remember restoring the phone will erase contacts, calendars, photos and other data on the phone, but will restore automatically backed-up information including text messages, notes, call history, contact favorites, sound settings, widget settings, etc.
Source: iPhone Hacks