I'm using objPDFCreator.cOption("AutosaveFilename") feature. If you assing filename with extension then PDFCreator will add another extension like this: "filename.pdf.pdf". This bug occurs under Windows 7 OS only. Under XP it works fine.
I have seen scripting samples and there filename without extension is bypassed.
Anyway I suggest to fix this issue and accept filename both with and without extension.