Open Project Properties window.
Select ICD 3 under Categories.
Select Clock from the Options Categories combo box
Only on PIC24/dsPIC33 devices: Use the internal fast RC (FRC) oscillator in debug mode for clocking instead of the oscillator specified for the application. This is useful when the application clock is slow. Reprogram after changing this setting.
Checking this box will let the application run at the slow speed but debug at the faster FRC speed. Peripherals that are not frozen will operate at the FRC speed while debugging.