So I reboot in Windows, hook up the gadget by USB cable, and run the software client, then backup the data on the phone to the computer. Opening the .nbu in a text editor, you'll find a lot of base-64 encoded data (that's any photos you backed up), but towards the end of the file...are all contacts that were saved to the phone's persistent memory, in standard vCard format, just separated by a line containing two tabs, a plus sign, and a letter. Like this:
(Phone numbers changed to protect the guilty)
If you just split out the vCards from the file, whatever you try to import them with will choke after the first contact. Get rid of the lines containing the funny characters and tabs, however, and you will find that a perfect multiple import is possible. Depending on how many contacts you have, you may want to do this with a scripting language, or just find and replace.