"download" button is disabled

Question

I am testing Keil MDK5 and created my own simple nRF51422 project (not from the sample), hello world type of code. But the "download" button is disabled.
The J-Link is configured correctly, in the debug settings, I can see the J-Link, also nRF51422 device. 
 The sample project is OK, I can download no problem.
I also compare the project setting between the sample project and my own project, I couldn't see anything different related to flash download. 
 My other computer is running MDK4. Never had problem with download.
Just curious about MDK5, so I got another computer to try it out. Now got into this basic basic problem :-D

Paul · Accepted Answer

I figured it out by myself :D 
 In "Options for Target"/"Utilities", I had to uncheck "Use Debug Driver", click "settigns" and manually select JLink. Bingo, "Download" button enabled. 
 Then I can check "Use Debug Driver" back, "download" button is still there. 
 I guess there is a bug in MDK5: With "use debug driver" checked, the initial "value" of the driver is "null". After I manually selected one, it got a value. 
 I am happy now. Just one of those annoying things :p