Hi there,
I wanted to say that I, too, am having major problems printing from snow leopard, using the UFR II 2.0 driver to my MF4150 machine from Canon. What is happening in my case is that the printer will usually print the first page of the current print job properly, then, however, it starts mixing up the current print job with snippets of the previous print job--so these two documents end up being jumbled together. This happens regardless of whether I am printing a pdf, a microsoft word document, or an email, and single-sided versus duplexing also makes no difference. So, the printer portion is useless at present. It's really frustrating and disappointing. The canon technical support has essentially said they are not aware of this problem and that it must have to do with my computer somehow rather than the driver. I don't really know what to do. If anyone has found solutions, please let me know. That printer was a big investment for me...