UPDATE
Ok - I've found out the source of the problem!!
I'm developing my app in xCode5.. Once in a while I open an older version of xCode with an older version of the app for some code references, so the problem happens when both projects are opened simultaneously.
The FacebookSDKResources.bundle
does exists on the older version of the project and this is the cause!
Hope it'll helps someone.
original answer
I'm not really sure if this is what solved it, since I left it as it was for a while and the next time I checked those log messages weren't there, but the only thing I do remember changing was the fact the I made my FBLoginView instance a singleton, so there was only one instance of it.
Worth the shot if anyone is dealing with the same issue.