At one time, I was having a lot of problems with ICSP programming of PIC16F628A chips. I had tried several different types of programmer circuits without resolution. Eventually, I found the solution to my problems when I found this page:
http://www.embedinc.com/picprg/icsp.htm. In particular, the topic near the bottom of the page entitled
PGD to PGC Crosstalk was the relevant portion. Adding the capacitors and resistors as described took care of the problem. Going back and looking at that page again just now, I see that this issue is said to be especially likely on dsPICs which is what is involved here.
NCR once refused to hire me because I was too short. I'm still waiting on my growth spurt.