Dropbox upload error

We're having trouble getting Dropbox to work. We have Omeka installed in a WebDAV environment, and after copying the files to the "files" directory, attempting to upload a file from Dropbox generates the following error:

"The file '4A-05-01.jpg' is missing and could not be ingested., The file '4A-05-01.jpg' could not be ingested because it is not readable."

The correct permissions are set for the appropriate directory. We have no trouble with uploading any other files through the "Add Item" interface, and all are standard .jpg files.

Thanks!!

This problem has been resolved. By turning on the error logging, I saw that it was apparently related to an "open_basedir restriction." After I asked my sysadmin to see what he could do to fix that, it still didn't work but at least I got a MIME error instead, which I was able to work around by disabling the "file upload validation" setting.