Having problems uploading an image/pdf

I am getting this error when I try to upload a PDF using the Media tab:

Warning: copy(/var/www/domains/reidar-bratvold.com/docs/wp-content/uploads/A-Game-Theoretic-Approach-to-Conflicting-and-Evolving-Stakeholder-Preferences.pdf) [function.copy]: failed to open stream: Permission denied in /var/www/domains/reidar-bratvold.com/docs/wp-admin/includes/file.php on line 348
176

Does anyone know how I can resolve this problem? I think earlier the images got uploaded in to folders by dates while I ticked that away now. Maybe this could have caused this? I want all the pdfs and images i upload to be saved in the Uploads folder and not in any subfolders.