Started flashing the other night and it finally went away the next morning going to work, this is on a '00 X AWD 5.0.

Along with this the drivers door won't open or unlock(pad, key, or keyless) from the outside.

 

Regarding the OD light... When it's flashing, you should notice the trans shifting harder. Essentially, it senses a problem and goes into 'limp/cripple' mode. It's not good for the trans to drive it in that mode. Although the light is out, you should pull the codes to see what is stored.