The same setup works good for P89C51RD2BA, but it does not work for P89C61X2BA.
Both CPUs are PLCC package, and are pin-to-pin compatible to each other.
The 66x match the Rx2H re ISP, not the non-H

I have used a Capacitor Reset circuit: C(10uF to Vcc).
The "H" chips are VERY sensitive to the reset and the errata states (in nice words) "if you use capacitor reset you are screwed".

There is, however, a solution:
A factory fresh chip arrives in ISP state and if you at that time install NoTouch (see my user page) you will never have a problem. NoTouch can NOT salvage chips with the vector blown.

Erik