My apps on my iPhone do not open, what can I do to fix this?

They open for around a second, but then immediately close. I tried un-ticking the Sync Apps option on iTunes, I also tried restoring, resetting, signing in and out, deleting and re-installing apps and even downloading another app to try and resolve the issue. I've looked everywhere and found no answer. The iPhone is the 3G and was unlocked, but legitimately via iTunes.

Are you jailbroken? If not try jailbreaking.