I recently upgraded a jailbreaked iPhone 3G to 3.0, everything works fine except for non-stock applications. Lauching any of those applications cause them to open and quickly close... Considering the really nice custom apps, the situation really sucks. I know I could restore and it would probably fix the problem, but I want to avoid that option. Any ideas?

As a side note, I've done the same with an iPhone original, and the same scenario happened (i.e. the apps didn't start). I fixed it by downgrading to 2.2.1 and upgrading back to 3.0 (since an unlock was necessary).