Sometimes TP wont charge? How to fix?

[kinesis]

Sometimes when I plug my TP in to the charger it will not charge (eg the battery icon does not change to a charge icon). It gets annoying when you plug it in, are about ready to leave and check it and the battery is fully drained hasnt even been charging at all. One way to workaround this is to hold the power button, turn the device fully off. Then you'll notice the touch pad light up so charging has begun, then you have to turn the unit back on.. Why is this and how do you fix?