So I contacted UPS about this, and here's the response I received:

Dear Tim,

Thank you for your email. Unfortunately, our tracking system does not indicate the reason for the delay. Our records show your shipment is currently in transit to its destination, and has been rescheduled for delivery on 1/7/08 by the end of the day.

For the latest tracking information, please continue to track your shipment at the following link:

http://www.ups.com/tracking/tracking.html

If you do not receive a delivery attempt by the rescheduled delivery date and your tracking number does not contain any further updates, please contact your shipper to initiate a shipment investigation. I am sorry that your shipment has been delayed, and I sincerely apologize for any inconvenience associated with this delay.

Please contact us if you need any additional assistance.

William Miller
UPS Customer Service

I'm appalled at the quality of customer service here. No offer to correct the situation was made, and I was essentially told to go check the tracking for the package myself. GRR!