Hi. After extensive headaches, I actually am the first person to report this issue on the DG2 and its cause to Verizon Wireless and Motorola. (According to them, anyway....)
The phone code programmer reversed the operation of the keyboard backlight in the Gingerbread update. When the light sensor "sees" darkness, it turns the keyboard backlight OFF instead of ON and vice-versa.
The temporary fix to this is to physically turn the phone toward a light source. The keyboard lighting will come on, and luckily stay on, until the phone goes into standby mode.
If you are in a totally dark place, if you put your hand over the touchscreen while the screen is on..... enough light may be reflected back into the light sensor to trigger the keyboard backlight.
Gingerbread, by the way, is full of a ton of critical bugs. I insisted Verizon do something about the problem, and they sent me a Droid Global 3 at their (Motorola's) expense. I should add I buy the additional insurance.
I am now noticing the keyboard backlight cycling on the DG3, and have not figured out a cause yet. The keyboard light on the DG3 does not lock on once turned on like the global 2.