Hi Mark
There is no interface.log included here in the post, but it is better anyway not to publish it here but to send this to me via email since it may contain confidential data as well.
But also if you get a 500 Internal Server Error message, there might be more useful information in your webservers error_log (the one where jOpenSim is installed).
The date issue in groups (last online usually shows 1970-01-01 which is the linux timestamp 0) is an issue from flotsam groups (where jOpenSim hooks on) not sending this value to the viewers in the correct format. Unfortunately that's why it cant be solved by jOpenSim in any way.
But OpenSimulator v0.9.x is on the way soon ... let's see what they will come up with in this matter
Greetz
FoTo50