A couple things to try:
1st check the backlight settings
Turn on Backlighting and Control Brightness
To use your device in dark environments, enable the automatic backlighting feature:
- From the Jump screen, press MENU then select Settings > Battery & Display.
- In the second group box, select the Turn on backlight when using device check box.
- Highlight, then select the Brightness slider to open it for editing. Roll the TRACKBALL right to increase brightness; roll the TRACKBALL left to decrease brightness. After you've made the adjustment, press the TRACKBALL to exit edit mode.
- Select the length of time you want backlighting to stay on from the Turn off after pop-up menu.
- To use the device's light meter while the backlight is on, select the Use ambient light sensor check box.
- Press JUMP to return to the Jump screen and save your setting.
Now, when you press any button or key, or flip open the screen, backlighting will turn on for the set amount of time. Note that as long as you press a key or button before the set time elapses, the backlight will stay on.
- Even if you have not selected automatic backlighting, you can turn on backlighting at any time by pressing MENU + JUMP . The backlight will remain on for the time specified in the Backlight Turn off after pop-up menu.
- When in key guard mode, you can turn on the backlight by pressing the RIGHT SHOULDER button.
If it still does not work, then you can try resetting the flex cable to the lcd.
Reseat the SidekickFlex cable
If that doesn't fix it then a new lcd assy will take care of the issue. they run about 45 dollars on ebay.
Sidekick LCD screens