First, make sure you have the most up-to-date version of the Facebook for iPhone app. Go to the App Store on your iPhone, and check the Updates section. If there's a newer version of the Facebook app you don't have yet, it'll be listed there for you to download.
If you continue to have trouble with the app, check the Facebook for iPhone Page for the most recent updates on known issues and new builds. If your problem isn't listed, please submit a report.
If you continue to have trouble with the app, check the Facebook for iPhone Page for the most recent updates on known issues and new builds. If your problem isn't listed, please submit a report.