Frequent Login to Facebook-Why?

I have a iPad 2 with IOS 6. I am having to log in frequently to Facebook, sometimes several times in an hour.

When I am prompted to relog in, the email shown as the account number and the password is incorrect so I have to reenter the new account number and new password, then everything is OK, until the next relog prompt.

I changed my email and password some time ago and have gone through the FB account info and removed all instances of the old account number (email address) and password, but the problem persists. I suspect the IOS 6 upgrade.

Any ideas would be welcome. I only have this problem when using the mobile FB app, I do not have it when using my desktop Mac.

Sent from my iPad using iPF