There were some earlier reports today on Reuters which quoted Nokia as saying that software testing problems had cropped up, and they needed a couple more weeks to get things right.
Anyone who remembers the original N-Gage's disastrous launch will appreciate Nokia's nervousness about launch problems, so it's perhaps understandable that they'd be very keen to make sure things work properly.
It's worth emphasising that the launch date of the Next Gen isn't that important because tens of millions of people have already bought the hardware. All that will happen on the launch day is that the N-Gage game download application will become available to the public, something they can download and install in a matter of minutes. There won't be any midnight queues in games shops as games shops won't be involved in Next Gen N-Gage at all.
The Next Gen games themselves are being sold entirely as downloads, so there was never any question of people buying them as Xmas pressies. The only physical items related to the Next Gen N-Gage platform are the phones, most of which have been on sale for many months.