Hi,
Its too delayed reply, but today only I got the same message. I just noticed the error on screen (after enabling debugging mode)
Fatal error: Cannot redeclare make_log_url() (previously declared in C:\inetpub\vhosts\domain\httpdocs\course\lib.php:30) in C:\Inetpub\vhosts\domain\httpdocs\course\lib.php on line 97
If you see the inetpub (the I has a different case), so I corrected my config.php and changed the I to uppercase for $CFG->dirroot and $CFG->dataroot
Mainly this error will occure if you have a Windows server.
I hope this will help others.
Cheers,
Jaswant