I am sorry to hear you are getting this error. I took a look at your account and the email called "Campaign Created 2014/07/16, 12:55 PM", is this the email you were getting the error with? It sounds like a character could be the issue but the email above has already been sent.
It may have been a character in the subject line. If you would like help figuring out what the cause was please let us know what the text said in the email before.