PIC24 PLL configuration
I don't know about all the parameters you've mentioned, but I know I ran into a problem when I accidentally set things up so I was above 70 MHz on one of the newer 70 MIPS PIC24E parts.  I brought it back down to 69 MHz (leaving a little wiggle room since I was using the internal oscillator), and everything worked fine again.

BTW, to avoid you're having to ask, I don't remember anymore how far above 70 MHz I was.