uploading images is not working. but great plugin!!

this is what I have been looking for!!!! very great.

I have a problem.
I installed my buddypress on 2nd blog like this.
http://codex.buddypress.org/user/install-buddypress-on-a-secondary-blog/

But It doesn’t upload my attachment files such as pictures.

It show files on preview but broken image url.

http://domain.com/2nd_theme_name/wp-content/uploads/sites/2/1368962632kangwongosung2.jpg

anther correct uploaded url (uploaded from admin page for testing)
http://domain.com/2nd_theme_name/wp-content/uploads/sites/2/2013/05/click_2008061801513524-1024×669.jpg

/2013/05/ <—- missing this folder name.

please let me know how I can fix it. I really really need it!!

thanks for great plugin.

and Any news for premium features? I am really looking forward to seeing it!

http://wordpress.org/extend/plugins/social-articles/