I am VERY new in this. This is my first post.
My NXT used to work well (just rechanged the battery too!). Today I am trying to connect the
Bluetooth device to my laptop, and I cannot make the NXT screen visible so that I set the Buetooth on and go to to do the
rest of the stuff to connect my laptop. What is wrong? How can I set the NXT to visible?

Thanks, John

What do you mean by "make the NXT screen visible"? Do you mean the physical LCD display on the NXT becomes blank? I have an NXT brick that does that from time to time. The display will go out and sometimes it will come back. Sometimes, it is only partially out. You can still see some pixels lighting up. I read some threads somewhere on discussions about some NXT LCD displays may be defective (loose connection or something) although I can't find the thread any more. I opened my NXT up but couldn't find anything visibly loose. Since then, I bought another NXT and that one doesn't have any problem. For the other defective NXT, I usually connect to it from my laptop via Bluetooth anyway so I opened the remote LCD screen on my laptop to see the display.

You should contact LEGO for a replacement. This is a known issue with some bricks. Don't mess with it, just get a new one from them, they will be happy to replace it.

- Xander

I've seen this happen a lot if people leave their display exposed to sunlight or the elements for too long: the crystals can physically get damaged. That may not be the root of your problem, but it's a thought.