walla210,
Welcome to the B&O community!
As you may already know the BS1 supports 480p and 1080i scanning formats. The only connection that supports 1080i resolution as input is the Top Panel component DTV IN.
As for the connections on the Top panel your PROJ OUT is a RGBHV Cable (15Pin D-Sub) connection for connecting a plasma screen or a large-screen projector, the DTV IN - Five sockets are available for connection of component signals from e.g. a high Definition set-top box: Y/G, Pr/R, Pb/B, H and V.
I went out and purchased a 9.84 ft. Silver Serpent VGA Breakout Cable, hd15 to 5 RCAs ( $79.95 currently ) from Better Cables ( http://www.bettercables.com/vga-breakout-cable.aspx ) seeing that, that is how I got a picture to show on my BeoVision 4 - 50. There price has gone down quite a bit since I purchased mine! This connects from the 15Pin D-Sub/PROJ. OUT into the BeoVisions RCA Inputs as well as the RS 232 Cable ( 6270808 ) USB in the Data connection port on the Rear connection panel of the BS1 into the serial RS232 input on the BeoVision 4. You may even just get a direct 15 pin D-sub RGBHV Cable as shown in the Cinema Installation Setup Manual. You can get the exact 15 pin designation in order to get a cable made if need be from the Cinema Installation Setup Manual as well.
Then via a Zektor HDS4 ( http://www.zektor.com/hds4/index.html ) component video and digital optical toslink/Coax audio switch I share the DTV In connection between my DirecTV Box and PS3 in order to run them at their highest resolution that the BS1 will recognize 1080i. The switch is then connected into the Top Connection Panel DTV IN as well as Digital Toslink out from the switch into the Rear Connection panel STB OPTICAL IN.
The DTV IN is the only connection that can handle the 1080i input. As for the rear panel panel connections on the BS1 you are limited to the lower resolution by the RCA (Composite) and S-Video (Y/C Seperated) which I believe is 480p.
Only other definite thing I can think of is that you need to enter the Menus of your BS1 and setup the attached Components as well as attached speakers.
I would also recommend heading over the the Products page and downloading the User/Service Manuals that are available for the BS1!
Conjureone
BeoVision 4-50 MkII, BeoSystem 1, Zektor Switch, DTS box, BeoLink Passive, BeoVox Cona, BeoLab 1, BeoLab 3500, BeoLab 6000, BeoLab 4000, BeoLab 4, BeoLab 3000, BeoMedia 1, BeoMaster 5, BeoSystem 3 Type 9621