Hello. I have already filed a bug about this driver not being able to print double-sided, because a memory leak, some months ago. Now, this has been fixed, but it still remains a problem:
Put the driver of Pixma iP3000 (gutenprint) as double-sided, long edge, then print a document with blank pages and written pages inside of it, and see what happens. You'll see that blank pages are just ignored, and not printed, but then, white pages glue together, so no blank pages are produced. This has a drawback, also: the first written page after a blank page gets printed just after the last written page before it, with no blank pages in between them. This makes an odd thing happen: this page gets printed rotated, so they all then became disordered after it. You have to reprint all the work if you need to have even pages on the left, and odd ones at the right, for example.
Please, try and see!!
Could you attach a document (openoffice or other) to test your bug ?