They have said
For any users with either Multiple (repeating) messages, or a Runtime Crash during Send/Receive:
I apologize for the inconvenience, and assure you we are working hard to correct this.
We are currently investigating the cause, and will inform you know as soon as we have a solution.
I'm now sure how they can fix it unless this application is connecting to Incredimail's server which would explain why this issue just started happening out of the blue.
Just thought I would let everyone know in case some of you do tech support for your customers and they call you with this issue.