Sounds like the Orei has a slightly confusing UI:
This is a quote from the Amazon.com review page for the device : http://www.amazon.com/XD-990-Composite-Multi-System-Video-Converter/dp/B0062BS09O
The device does what it should and with good quality, and that's the important thing.
I am using it in Israel to bridge between a DVBT STB and a US version of Panasonic Viera HDTV. Now everything is great and I am happy with this buy. But (the big tip is bellow)....
I managed to set it up initially quit quickly, without recognizing that I had more luck than brains
. An electrical power interruption changed that, as settings got reset and I had to set it up again.
I couldn't, and contacted Orei tech support. They were very helpful explaining how to use their poor interface (a big word for 3 buttons) to set up the device. I should mention that none of this explanation is anywhere to be found in the device literature (another big word). They promised the next batch will be more user friendly...
There are 3 buttons on the device: one for type of connectivity you use (composite\HDMI), second for output-resolution (720p/1080p), third for format (PAL/NTSC).
There is a special way of using those buttons and if you don't know it you can't use the device:
Single press on any button is good for displaying the current relevant setting on the screen (that is if you see anything on the screen, otherwise you are working blind until you get the setting right and be able to see anything).
To actually change the mode (on each button) you need press the button twice and quickly (slowly will just show the information twice). That's the big secret. It's a shame I almost throw the device away because of a thing like that.
Sounds like you want CVBS as your input format as you are using a set top box with a Composite RCA output (which is presumably PAL 50Hz) You then want to select either 720p or 1080p as your output format (probably doesn't matter if your display can cope with either). You then want to select NTSC as your output format.
In each case it sounds like you have to press the button TWICE quickly to change mode, the first press just displays the current setting ?
Also the Amazon reviews have quite a few people who received faulty units - so that might also be a possibility?