Can you let me know what action type and object you've configured? Specifically, what extension are you using for the object (Joomla Content, K2, JomSocial, etc) and what 'action' are you trying to trigger on that object?
If you have a URL that we can test on and instructions on how to trigger the action, that would help as well.
Geting there anyhow
I'm not sure what you mean here.. is the action still posting to the user's Timeline, even with the error, or something else?
Thanks,
Alex