As I have reported lately I obtained a Nikon D90 DSLR some weeks ago. Gphoto2 (and other application depending on its functionality like digikam) didn't recognized the D90 in PTP mode and the camera can't be configured yet to offer the SD card as a mass storage device.
In the meantime I found out that the D90 does work with gphoto2 in generic PTP mode - at least this is with Ubuntu Intrepid on my x86 laptop while Debian Sid on my G4 PowerPC fails to detect the D90. It detects the camera, the pictures, loads some 1 or 2 thumbs and hangs.
So, I don't know whether there are some differences between Intrepid and Sid (gphoto2 is the same version as reported by dpkg - with the exception of the "ubuntu" version string in Intrepid) or a PPC vs x86 issue - or maybe a kernel issue as this is different between those two machines as well.
This is just a quick note, mostly for myself. I'll try to get more details within the next days and file a bugreport. But if you, dear lazyweb, have some additional pointers for me, I'd appreciate those! :-)
UPDATE: problem solved as you can read here.