My MPLAB X IDE debugger gives me an error whenever I try to debug my PIC24 Explorer 16/32 Development Board
First, make sure your XC16/32 compiler is up-to-date. Then disconnect your PIM from the board. Then plug in your micro-B USB connector into J18. The PKOB enumerates as a HID class so there should be no drivers needed. 

Do you see the following inside MPLABX? 



I've also found that sometimes this error can occur if the power supply is insufficient. Consider plugging in the barrel connector at J12. 

See the official docs for more info.