Facebook phishing problem

First of all, sorry my english is very bad.

I have a problem with facebook

I have a web app that ask user to register with facebook or twitter or some other social network.

When the user is authentified is used token for publish picture with their facebook account.

During one week no problème but after when i would like publish a picture in their wall i have a facebook message like this : " The authorization has been revoked. Reason: Error validating access token: The session has been invalidated because the user has changed the password." But the user don't have change her password.

And when the user would like to go in facebook. he have a message like someone tried to access your account ... it looks like phishing

I have change my facebook application setting :

Server IP Whitelist: my server ip .

And no change.

Somebody know what can i do, to don't have this message of phishing. What i do wrong ?

I have already ask for help in stackoverflow in this thread :

http://stackoverflow.com/questions/1...-like-phishing

but no help.

I someone have informations thank for reply.