Weird - I just replied to your other thread, then the whole thread disappeared! Hopefully that won't happen this time.
Anyway, you need to change the resolution on your AT-163 (not your monitor). I don't own an AT-163 but they're very similar to the iView and HomeWorX boxes, so these instructions for the iView should work for your AT-163 as well:
Press Menu on the remote, then cursor right to the Picture menu, then down to the Resolution setting. Now cursor right (each time you do this, the screen will go blank for a few seconds - don't panic) to the 1080p(60Hz) setting. That should be the correct setting for your Samsung monitor. You can then exit the menu and the "not optimum" box should not appear.
I'm assuming you can see the AT-163 menus, despite the "not optimum" box. If not, hook the AT-163 up to a TV temporarily, follow the above instructions, then hook it back up to the Samsung and it should work.