Driver suddenly unable to email in production system

Hello,

We have an application that is called from a web service. The application runs as a Windows service logged in as a user. The application prints customer statements using the PDF-XChange API and is supposed to email them via SMTP. However, the system is misbehaving. If I log into the machine where the service is running, when a request comes in, the PDF Save Save As... dialog appears. This should never happen, as the PDF should be emailed without user interation. Please help. This is a production system.

Thanks,

more details:

Business Motion Graphics Example