the Incredimail support at http://www.incredimail.com/english/help/support.aspx ?
By any chance are you running 64 bit Vista rather than 32 bit? If so, there is your answer - IncrediMail does not yet fully support a 64 bit OS
I have used it for years. It would not open easily for about a week and then stopped completely. I tried to download \incredimail2. It downloaded, but would not open. I got the message 'the application tray stopped working.' Then, I got a second message saying 'there was a critical error and the application had to close.'

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