I have a similar suggestion to one that was posted here. This should apply most specifically to sites running on Linux/Unix servers.
In your WordPress Admin area go to Settings, then Miscellaneous. If the directory is set to /wp-content/uploads change it to wp-content/uploads. In a Unix environment that might be telling it to look for the folder in the root directory, which normal users usually do not have permission to use. If you take out the first slash it should tel it, from the current directory, look. for wp-content. This may not work for everyone, but it’s one possible solution.
