Users seen as offline

Hello, I am running Openfire 3.7.1 on Ubuntu, and everything has been great until the past couple of days where users are showing up as offline (Pandion), but actually can send and receive messages. Any ideas on what I should be looking for?

Thanks

What about JVM memory status (on the home page of Admin Console, hit refresh few times to see how it changes)? Also, maybe there are some errors in te error.log (maybe memory related).

The jvm usage seems to be fairly consistent at about 20% - I have seen some discussions about folks having problems with the most recent Pandion client, so I am thinking that may be the culprit.