Second hand T40 and warranty

[tsukiyomi]

Hi

I have a second hand T40. It was bought from person that lives
in Germany. My Thinkpad has a international warranty that ends
in september. I want to give my unit back to the service because:
- the usb port stopped working in usb 2.0 mode
- the laptot tends to turn off LCD screen while holding
with one hand in the corner of the unit (mobo flexing).
IBM Service in Poland says that I have to deliver the laptop with original box, and some kind of a invoice or other proof of buy. As I said before I don`t have such documents because the laptop was bougth not direct from IBM. What should I do ? I know that the warranty follows the laptops serial number so I don`t need to have any other documents. Is that statement correct ? Anyone had any experience with getting service for their second hand Thinkpads ?
Or should I contact IBM Germany and deliver laptop to the German IBM Service ?

TIA

[AIX]

Look here:

http://forum.thinkpads.com/viewtopic.php?t=21759