Hi All,
This is caused because your facebook account goes into a deadlock condition because of its inbuilt (crappy) security feature. It sees that you have logged in to facebook via two mobile clients simultaneously (in this case your inbuilt fb client & the ovi app), and restricts login to facebook via any mobile client temporarily (in our case permanently ).Facebook says you need to do a normal web login if you come through this problem and it will auto unlock the mobile client login in the process. This so called "unlock process" does not happen sometimes. Or may be the system disables the mobile client login permanently in a random fashion. I have reported to facebook like 10 times but no revert. They dont have a dedicated support email DL to attend for tech issues.
This aint nokia's problem because it works if u try to login with someone else's account.