I have the same issue with my brand new Dell Inspiron 15.
I spent 4 1/2 hours with Dell warranty department trying to troubleshoot this very issue. They remoted into my computer and did an exhaustive search. The final result was that it is not a hardware issue, but rather a software issue.
Now for the fun part... the computer warranty does not cover software issues. So, they said they can fix the problem but it will cost me over $300.00!!
What a joke this is. Dell does not stand behind what is clearly an inherent issue with their product.
I wish I had never bought a Dell product. And never will again...