Wow, thanks Daryl and Wroot. I've ckecked the logs, and that happens many times when the issue cames:
2014.07.03 15:33:24 org.jivesoftware.database.SequenceManager - WARNING: failed to obtain next ID block due to thread contention. Trying again...
2014.07.03 15:33:24 org.jivesoftware.database.SequenceManager - Failed at last attempt to obtain an ID, aborting...
2014.07.03 15:33:26 org.jivesoftware.openfire.privacy.PrivacyListProvider - Error loading default privacy list of username: uru-colet-andreia
java.sql.SQLException: ConnectionManager.getConnection() failed to obtain a connection after 11 retries. The exception from the last attempt is as follows: java.sql.SQLException: Couldn't get connection because we are at maximum connection count (25/25) and there are none available
at org.jivesoftware.database.DbConnectionManager.getConnection(DbConnectionManager .java:151)
...and goes on.
I will consider to go to 3.9.1, because the only problem that I had in the 3.8.2 was the java memory heap (i can't set it to more than 1536 MB and I need at least 2048)
Thanks, one more time 