When plugged in, DX won't charge all the time.

[BKSinAZ]

Sometimes when I plug in my charger, the phone wont start to charge.
Last night I had 40% of battery left, so I plugged in the phone and the DX would not start to charge. I had to repeatedly unplug the phone and plug it in again till it would start to charge.
What could be wrong?

Second time this is happened to me with the 5 day old DX.

 

[KevinWP]

It's a short USB Cable, and you may be tugging on the power block without realizing it. Be sure if this happens again to check to ensure the power block is plugged into the wall or extension cord. It may have wiggled loose.

(Mine came loose just yesterday which is what made me think of this).