As others have said, check your ICSP connections. Then check again. And again. Seriously. I have spent far too many hours fannying around with this interface only to find it's a schoolboy error.
I have made two different PCB's with this PIC and checked the connections from both boards to the programmer multiple times. But I'll check again to be sure.
Are you powering this from the PicKit3-a-like or is it self powered?
I have tried both.
If pwoered from the PK3, check the current demands of the rest of the circuit are minimal.
I have not populated the whole board yet, just what's needed to get the mcu running, so no current demand from the rest of the circuit.
PICs are not alone, debug interfaces are the perennial weak link of flakiness in embedded debugging and programming. Once you've got it figured out it should be reliable though.
I have used this programmer for maybe two years now and I have also found it to be reliable. No problems in the past that wasn't quickly resolved as soon as I figured out what I was doing wrong.
In the meantime can you tell us what OS you're running, and what MPLAB you're using? There were some versions of MPLAB X that were just awful at detecting PK3s, I wasted a frw days of my life on that too. Screen prints of your error and environment will help.
Running Windows 7 64bit. I normally use the standalone programming software, I only downloaded MPLAB when I started to suspect the standalone software didn't support the device.
I'm using MPLAB X, either 2.05 or 2.30, I will check whan I'm back on my computer tonight. I'll get some screenshorts too.
To clarify: the PK3 is detected, but not the PIC.