Can anyone think of a reason why I would need to login twice when my site is closed (XOOPS 2.0.7.3)?

Strangely, this is only the case with the (nearly) production server (UNIX) and not with my test server (WIN2K). I get past the first login and to the home page (it's the "home" module), but selecting any menu item on the page brings back the site closed login page.

If I log in again at this point, everything is fine. Or if I back the browser out to the first site closed login screen and login there again, it also works.

I have double-checked (as best I can) that the files are the same on both servers. The only real difference I can see is that the test server has the XOOPS code in a sub-directory (public_html/xoops_html : where the virtual host name points to public_html) whereas the hosted production server has the XOOPS code in public_html, which is the target of my domain name on the server.

Thanks.