When auto-save to JPEG is enabled PDFCreator creates one JPEG file but prints all the pages to the same file, meaning it siply streams the output to a single file.
If you search for the "JFIF" string inside this JPEG file you will find it many times, the number of times being the number of pages.
The bug might be due to the fact that the filename ends with the string "%d" (when "One page per file" is selected) which probably makes the output redirect the stream to the same file. Anyway it doesn't matter if "One page per file is selected" as the files still get concatenated into a single file.
20090929131530%d.jpg <-- example of file naming.
Regards,
Dragos