Welcome to the AndroidForums, CM1984.
I've moved your thread to the Milestone X forum where the good folks in there should be able to give you some good advice.
Cheers and good luck!
edit: oops! I just saw your other thread and that there's not a lot of threads here in the Milestone X forum
. Which is probably why you posted in the Android Lounge...
I own a Droid X, which I understand should be very similar to your Milestone X, but I'm not sure what it could be. I'm guessing some kind of loose connection / short maybe? Is the battery loose behind the door?
You could try a different battery I suppose... Also, you could search in the Droid X forums (try the http://androidforums.com/droid-x-support-troubleshooting/
first to see if someone has posted something in there.
If you do end-up posting in there, be sure to indicate that you know you are posting in the DX forums because the devices are similar (I believe) and that there's not many threads in the Milesone X area.
Ping me on PM or reply back to this thread if you get any grief about posting in the wrong area, but hopefully they'll be understanding if you explain things.
Cheers (for a second time