One can find tracker items that go back as far as 2008 and version 1.8 of Moodle. Browsing through them one might find resolution to problem ... but ... tracker says can't replicate. And, the issue seems to 'go away' (but not for all). Google for the subject in this thread and you'll find 'em.
Assuming your server meets requirements for PHP/MySQL for version 2.8 ...
Does config.php file exist ... it must, since you are on admin user screen ... if it does, *try* this while on that admin user creation screen ...
In moodledata create a directory/folder called 'sessions' IF it doesn't already exist. Set permissions liberally but do make sure it belongs to the web server user and that user has rwx.
edit config.php file and make sure it's using 'files' rather than DB for sessions.
Add a line: $CFG->dbsessions=0;
The next click that should go into affect. That should force moodle to use the sessions directory to record session info rather than DB (don't re-call what the default for 2.8 is right now).
IF it reports same error, hit return in browser to get back to form. Check the sessions directory to see if there is a file in there now ... ie, your session. Then try the form again.
Fingers crossed!
'spirit of sharing', Ken
Tried all the suggestions and nothing worked. So i installed 2.6 an then upgraded to 2,8. That worked.
There is a bug in 2.8 web installer. I tried on 3 different web servers and got the same error using fox or chrome.