When I bought my DroidX at Costco, it came with a case which has a magnetic closure. I asked Motorola if it mattered how I inserted the DroidX in the case and got the following reply:
Thanks for reaching out to Motorola. Iíve reviewed your e-mail and Iím ready to help.Any thoughts?
We do not recommend using a holster with a magnet for the Motorola DROID X.
If you notice that your phone is displaying a screen that you are not familiar with or your backlight continuously stays lit even when you have adjusted the backlight settings your phone may be in close contact with a magnet.
There are certain components within the phone that when placed in close contact to a magnet will trigger a different screen configuration and cause your phone backlight to stay lit.
Tip: Several phone holsters contain magnets that may also cause your display to change and your backlight to stay continuously lit.
This is not a defect of the phone.
We hope that you find this information useful and look forward to assisting you in the future.