Depending on the dashboard version you were on before you started, you may need to perform an update in order to get Avatars/Kinect working correctly.
If that is the case, put the USB key back in your PC, and delete the files from it.
Now place the $systemupdate folder from the official 2.0.14XXX.0 update, on the USB Key
If you chose to create your NAND image with DashLaunch patches included (as you should have), then rename
$systemupdate to $$ystemupdate otherwise the update wont install, because DashLaunch is configured to block updates by default.
Make sure your xbox has some storage space for the update files, like a HDD or internal memory
Insert the USB key into the 360, and allow it to perform the update.