6
Yup, looks like the xoops_session table in your database.
Your web host should provide you with a tool called phpMyAdmin accessible via your domain control panel. If they do, access it, and then access your XOOPS database. Get it to list all the tables for you and you may well find, about half way down that the value for xoops_session says 'in use'. To flush it, tick the checkbox and then click on the Empty button near the bottom. Then log out of your phpMyAdmin and try to access the XOOPS site again. (This is all described fully in the link I provided in my last post BTW).
Try that.
One last point, it may well be to do with the HTTP_REFERRER issues with regard to your users firewalls and the fact that your XOOPS site has not been coded to ignore it. Do a search for HTTP_REFERRER Check and you'll find loads on theis site about it.
Good luck