You're certain you don't have the file class/xoopssecurity.php? XOOPS 2.0.13 shouldn't work at all without that file.

Note that it's in the "class" directory, not the "include" directory.

My god Dave - I am so sorry!! I am such a fool!!

For some reason, when I last did an FTP download of my site to my local PC that particular file was left behind. Not sure why, but it was. When I was looking for the file I was looking at my assumed 'mirror' copy on my local PC. When you said what you said above I thought I'd check my site using FTP. And there it was!!

I downloaded it, editied it like you suggested above, and everything seems to be OK.

Thanks again, and sorry again for wasting your time which I know is valuable to us all!!

No problem.