Jing users experiencing this issue will see a dialog window similar to this screenshot.
You may wish to review the Article located at the link provided, to make sure your Security Settings are correct, as this may be the cause of the issue:
Jing will not login to Screencast.com...
However, the best course of action is to try sharing your capture at a later time, as this usually resolves the issue.
If you've waited, but your Jing captures are still not uploading properly, please contact Technical Support.