Hey I've had exactly the same problem as everyone else but have sorted it. I don't know what is causing the exact issue, whether Jailbroken or not, although know for sure that on MY iPhone4S running 5.1.1 if I use Facebook 5.1 it crashes ONLY on the news feed and when using Facebook 5.2 it just crashes and won;t even allow me to login. I managed to obtain a copy of Facebook 5.0.1 online and had the same issues.

After hours of searching I have managed to obtain a copy of Facebook 5.0.0 and GUARANTEE that it will work without crashes. I reckon that in the 5.0.1 and later updates, Facebook must have changed something to work differently which has caused nothing but trouble.

I am happy to share the link and have it stored in my Dropbox account by following this link --> https://www.dropbox.com/sh/kkb98wu64in0jgk/4UMjfvUwD6. What I would appreciate for this is people to use this link here to sign up for Dropbox under an email account so I can get more space...--> http://db.tt/rROKgde . I really appreciate it!

Please comment to let me know if it worked for you but I'm positive it will. Just make sure you delete the existing app off your phone AND your iTunes on your computer, then download the Facebook 5.0.0 ipa, double click to add to iTunes then sync your device.

Glad I could help! Let's hope Facebook sort things out, what a nightmare hey!