Is the upload destination folder on your Mac's boot drive? If instead it's set to an external/network volume, please change the destination to your local drive and see if the photos are delivered successfully.
If this doesn't resolve the issue, please send us your Eye-Fi Helper log and Settings.xml file so we can take a look.
First, quit Eye-Fi Helper (look for its icon in your Apple menu bar). Then open this folder in your home directory: /Users/<your_username>/Library/Eye-Fi. (To open the Library folder on Mac OS X 10.7, hold down Option/Alt while clicking the Finder's Go menu and choose Library.) Once you are in the Eye-Fi folder, look for files called EyeFi, EyeFi.log, EyeFi.log.1, and Settings.xml, and attach the ones you find to an email to firstname.lastname@example.org
. Please mention this thread.
After you send the logs, feel free to re-start Eye-Fi Helper and/or Center if you like.
To anyone else who is experiencing problems with your Eye-Fi card or software, please contact us! We're available 10 hours a day Monday-Friday to help you resolve issues like these. http://support.eye.fi/contact-support/