Hello,
I have the same problem.
Strangely, it rarely happened in the past, but lately I encountered several error messages as mentioned in this thread when I use the linkback to an email message. It doesn't happen all the time for every message, but only with some emails.
As Pete P mentions, I noticed that there was a % in the email ID and it could be the same reason for this bug.
I don't use Entourage at all, only Apple Mail, and I have no idea if the person who sent me the message sent it through Entourage or not...
Is there any solution to avoid this bug?
Thanks a lot for helping,
Best Regards,
Gabriel