App keys (id and secret) get erased every time I visit the corresponding settings page

Hello,

I have installed the module and make it see the SDK file (patched the fpconnect.module as requrieed).

However, when I visit page
/admin/config/people/fbconnect/api-keys
both App ID and App Secret fields are empty, regardless of whetner I entered them or not.

I checkde that the 'variable' table has correct values for both firlds (i.e., those I entered).

Status report shows no problems for FB Connect.

How could I proceed in such a situation?