Log in error occur frequently

I`m developing application using xmpp framework in iOS and using open-fire server by MAC OS…

the day before yesterday, I patched open-fire new released version…that was the start point of my problem…

after the day, sometimes, log in error message occcur,

[Login failed: make sure your username and password are correct and that you’re an admin or moderator.]

so, I checked linked MySQL Database and modified Admin`s password…

this problem occurs frequently so i stress…

how can i do in this situation, many people say that re-start server is the best answer of this problem, but it doen`t solve this problem…

New version open-fire get some problems???thanks in advance…