Try the same as I said to blazinthu below in this post. First the downloads.php code change and it that doesn't work, the .htaccess changes from vB.com.
Have a look at
this post. Install the add-on trynksssj2 mentions and do the code change I proposed.
Please send me a pm with your forums URL and the username/password of a test account, so I can check it out.
There's a mass import feature in the AdminCP to import files from a directory on your FTP.
I know there's a DownloadsII extension for vBSEO available at their forums, but I'm not using any SEO mods myself.
All security tokens are in place. This is a problem with the large files. You will probably have the same when uploading large attachments in vB itself.
You can try this:
Open downloads.php
Find
PHP Code:
error_reporting(E_ALL & ~E_NOTICE);
Add this after it:
PHP Code:
@set_time_limit(0);
If that doesn't work, read #3 in
http://www.vbulletin.com/forum/showthread.php?t=268862 for more information (but disregard the my.cnf MySQL part, DownloadsII is only storing its files in the filesystem, not in the database).