With this guide, i will explain the different problems and solutions to the problems for the model i880 and i885 cell phone for nextel and boost mobile.
i880-i885

All of the following are hardware defects caused by the flip ribbon. Replacing the LCD Screens will NOT solve your problem. You will need to either replace the ribbon, or if you dont know how to install that part, replace the whole flip which would be easier to install if you are not an experienced technician.
1) Inner LCD showing upside down
2) No Backlight on LCDs
3) Blurred Pictures/ No image (white screen)
4) Camera not working (multimedia error)

All of the following are software problems caused by 3rd party applications or user faults. In order to repair such problem, you will either need to replace your unit (phone) with your insurance or take it in for repair. A reprogramming will be needed of the phone software by a professional.
1) Freezing on startup at the i880-i885 Screen
2) Not turning on at all, No Power (this may also be water damage)

How can you tell if your i880-i885 has water/liquid damage?
Unscrew all screws from behind the phones (note: i885 has a hidden screw behind the battery door opening switch, and both i880 and i885 have 2 screws under the screw
 plugs.) and open the phone up, check on the main board for the liquid damage stickers, if they are red or you see the board has rust on it, then the phone has water damage.

Whats the problem causing your phone not to be able to read your sim card even though you placed on in there?
If you placed your sim card in your phone and it still states "insert sim" then you either have a faulty back assembly which needs to be replaced, or your main board
has damage which is causing it to operate properly.