I have had a problem with the e-mail invoices and have managed to solve it, it is possible that someone of you spends(passes) the same thing to you, this way that this one is the solution that me has worked.
The problem was that e-mail was not sending and the response belong to time-out the server
if anyone else has found got some useful tips on how to get certain things working - please post them so the rest of the Simple Invoices community can learn from your experience