dirk, you need to connect a suitable usb device. run the command when it says waiting, then hold "u" on the keyboard of your n900 while you plug in the USB cable to the device. only after the USB logo pops up in the upper right corner should you let go of the "u" and if the drivers have been installed properly the flasher will place the new kernel on the device, should take >10s. i would wait and see if you can disconnect the device through the manager safely before just pulling the plug out. let the device boot or do what it needs to do after.

i bricked my device trynna figure this out.