I have a site that has no cache in use. I'll test the login/last seen times there. If I logout and then login my last seen times should be seconds off. If it isn't then I'll try and hunt it down there. If it's off as many minutes as your user's was I'll spend some time on that elapsed time function because I'll be using it later on.
Donate to UBBDev today to help aid in Operational, Server and Script Maintenance, and Development costs.
Please also see our parent organization VNC Web Services if you're in the need of a new UBB.threads Install or Upgrade, Site/Server Migrations, or Security and Coding Services.