hello again

I'm still having login problems on different sites on my webserver. On several sites, I upgraded from version 1.2.4 to 1.3.7 and since then, a login attempt says « /!\ Login failed ». Users at sites running RoundCube 1.2.4 have no problems.

A.L.E.C. said, I should fix the database. How can I do this? I couldn't find any instructions online...