Steve,
When I was writing the reply down below, I re-read your last reply and it gave me a better idea to ask you about first. Since you had a version of 2.3.1 already installed and went to update it, did you load the NEW files over the OLD ones? If you did, that could be your problem. It is always recommended to make a totally new web folder (you can keep the data one) and put the new upgrade there. The only OLD file to go in there is your config.php.
Hope this helps. If it doesn't apply then check the other ideas below.
AL
Steve,
I have two suggestions.
1. Are you able to check the permissions on your site files and folders. I have had a couple of problems in the past where just ONE file was set wrong because of placing it there after setting all the others and then forgetting to check the last addition.
2. When you are able to get in and change things, are you also able to do a backup? If you can, I would do so. Theeeen, I went and looked at your site, and at the moment it does not appear that you have too much there, sooooo, I would remove the config.php file and then trigger a new install manually by going to http://www.ilearnalot.net/ .
I have had to do that on a couple of installations. Only one of them also required me to empty the database before it worked, but I don't think you would need to do that.
You will be able to use the same database name, db user, dbpassword, admin, and admin password as the install will overwrite anything already in the db.
HTH,
AL