When a client loses the connection to the server without properly closing it, for example because of a typical cyclic DSL-disconnect or if the network-cable is pulled out, the server doesn't seem to recognize this and every message sent to this client is simply dropped until the client's timeout period is over and the status of the client is automatically set to offline.
I'm experiencing this problem at least since Openfire 3.3, but I guess it was always the way it is now. There are comments on the board dating back to 2005 about this. In Openfire 3.7 on Debian Lenny (x86_64) with Sun Java JRE 1.6.0_22, there is still the same problem. I think this is a horrible and often hidden bug and an unacceptable experience for users to drop their messages without any notice.
Please fix this soon!