Bottom line, it's clear to me at least that any 328p circuit using a series cap coupled auto-reset feature should have the reset diode installed for best reliablity.
Yes, I agree. I will be using the diodes on all my boards going forward.
I should have been more careful with the wording in my previous post in this thread. It would have been more accurate to say that on this particular board and with this particular chip
, the latch up problem wasn't exhibited using the Duemilanove bootloader.
@retrolefty: per your suggestion on that original "diode thread" I downloaded Bray's terminal (very nice application). I saw the same behavior on my boards (optiboot bootloader) that you reported, i.e., that a reset is triggered by any change in the DTR line when no diode is installed. After installation of the diode a reset only occurred when DTR went from low to high. No reset is triggered by changing DTR from high to low once the diode is in place.