After updating to iOS 4.3.3, a friend of mine could not launch any non-native application (i.e. he could open Settings, Phone or Messages while eBay, Amazon or IMDb crashed immediately).
Fortunately, we found this way to make it work:
Delete any app, download it from the AppStore again, restart that app, and not only it will work, all the apps work as before.
Source: http://home.wangjianshuo.com/archives/20110527_all_apps_crashes_after_ios_433_in_iphone_.htm
Yamanika 