1st... does the Xbox360 "sees" the DNS-323 in the "Video Library"
If NOT:
I would recommend doing a backup of you data before proceding
upgrade the DNS to v1.07 (or v1.06)
after the upgrade, hold the reset switch behind the DNS for about 30 second
This should reset the settings to default... (this will not delete/change data in the hard drives)
Create an empty folder in the root of the DNS
Go to the web interface of the DNS, activate the UPnP service
and select that empty folder you just created for the UPnP path
Save the settings.
Put 1 video file in that empty folder
back to the web interface, click on the "Refresh" button, wait till it goes to 100%
Your Xbox360 should now see the DNS-323 and video you added.
If you xbox360 DOES see the DNS-323 and the video files, but its to slow to stream (choppy video)
then it could be an issue with your network... in that case we need more info
Are you connecting the xbox via wireless?
how far away are you from the access point?
how many wireless client do you have connected at the same time...
what kind of router do you have.....