After reading your log, it would seem URL rewriting is not enabled. could you change your .htaccess to make it look like that :
Code:
RewriteEngine on
RewriteRule ^download/(\d*)/(\d*)/.*\.kepub\.epub$ fetch.php?data=$1&db=$2&type=epub [L]
RewriteRule ^download/(\d*)/(\d*)/.*\.(.*)$ fetch.php?data=$1&db=$2&type=$3 [L]
RewriteRule ^download/(\d*)/.*\.kepub\.epub$ fetch.php?data=$1&type=epub [L]
RewriteRule ^download/(\d*)/.*\.(.*)$ fetch.php?data=$1&type=$2 [L]
So loosing the IfModule tag.
It should trigger an error if URL rewriting is not really enabled.
You can also try to drop all the "^" before "download" it shouldn't matter in your case but who knows.