You seems to have installed an old Kernel 2.6 driver, its always important to install the drivers from the Feeds of the image, as well as same kernel as the image (DM800HDse Japhar images are now Kernel 3.2).

Probably a new clean installation, then installing from the feeds as you done and the wirelesslan plugin could sort out things.

opkg update
opkg install kernel-module-rt2800usb
opkg install firmware-rt2870
opkg install enigma2-plugin-systemplugins-wirelesslan

Admin