Codeigniter do_upload doesn't response in production server

[eluser]mF4d[/eluser]
[quote author="siptik" date="1347349567"]maybe you forgot to allow access to the folder in .htaccess?[/quote]
Thanks, but I didn't set any .htaccess. Is that the case? What should I set in them?
I think the folder can be accessed because the native php code I wrote to upload the file is working fine in production.