setup problem with Conia M550 DVD player - sound but no picture?

We were setting up Conia M550 DVD player but had a problem of being able to see only in black and white. So I went into Setup Menu of the player to try and see if I could fiddle with some setting. Whilst doing this I chose "General Setup" and went into TV submenu (I can't recall exactly but the other submenu was "interlace") and pressed "enter". This caused the screen to go blank, though the sound was O.K. Now, I don't know which menu I'm on as I can't see anything on the screen but I'm guessing that the DVD is sending video signals correctly to the TV.

If anyone has an answer I would be very glad to hear from you.