The error you get might be related to the following lines in the .htaccess:
<Files ~ "^[\._]ht">
Order allow,deny
Deny from all
Satisfy All
</Files>
I have the same problem because my apache setup doesn't allow me to do that, commenting out the above lines helped in my case.
To restore your old config just edit <dokuwiki>/conf/local.php and set $config['userewrite'] = 0;.