You broke the Invoice Journal!!
Hmmm...what did you do? A message has been sent off to the Invoice Journal gods and we will try to fix this error as soon as possible.
Please go back and try to do what you just tried to do again. If you see this message again something is wrong with the system. Please visit the forum and see if this is a known error, there might be work-arounds. Also, please only retry one or two times...we get an email for every error generated so please don't retry 20 times! :P