Incredimail is not bug free. It can cause issues.
After you've had your fun with it, consider removing it.
I belong to a few graphic sharing groups and from time to time receive the following error message, when opening one of these type e-mails. I don't have incredimail and some of the graphics are from users of the program.
I really don't know if I should be clicking on yes or no, but either of them then gets me to the body of the e-mail.
What would be the cause of this message?