An option is to use a mail forwarding service [...] Another option is to go to a UPS Store/Fedex Kinkos that accepts parcels on your behalf [...] You may need to drive over to the border to do this.
when my european N80 broke, I sent it to a nokia certified repair shop. they took it, and they themselves sent it to Nokia, which then sent it back to them, which in turn sent it back to me. maybe you can do something like that? drive to a nokia store across the border (not sure how close you are) and drop it off for repair, and come back and get it ?
One more thing I would recommend. I added my N900 to StateFarm's Personal Articles Insurance. It is about 40CAD a year and covers accidental damage and has no deductible. Its really a wonderful product vs the usual warranty service. I can PM you the name of my REALLY WONDERFUL agent if you decide to go for this. (You can put in almost anything on this policy, camera, laptop, etc and it covers theft, accidental damange, etc).
Ouch... sounds pretty bad, cusomer-service vice....Reminds me of german bureaucracy (and belive me... those guys can be a royal pain in the *****....
But to offer some help: do you have any friends and/or family living in the states? so that maybe they could give "their" N900 to repair....