I have just updated to 3.0, and installed Facebook, which worked fine, since doing that I have restored my iphone 3g to its old settings etc, now it wont even let me open the app, it goes to open then just closes.
I have uninstalled and reinstalled about 4 times now, anyone got any ideas?
I also faced the same problem few months ago, I restored my old settings and reinstalled all the applications. After that I rebooted my device. Then it worked smooth. I hope this may work for you. Try it!