OS: Windows 7, x64, Service Pack 1.
PDFCreator version: 1.7.3
When printing images with Windows Photo Viewer (WPV) as a default print application (default even when you install an IrfanView) without the /NOSTART option, a WPV print dialog shows first. After clicking a Print button, the file is queued and then converted.
With the /NOSTART option, no dialog is shown and no PDF is generated. It seems as if the print dialog is about to show but is probably terminated since the command line loses and regains focus very quickly.
PDFCreator process should wait for the WPV print dialog to finish.