Hi,

Did you try to read out the program memory from the faulty pic? How do you know you really had a problem? Do you have brown out turned on or off?

Sometimes if BOR is off and the pic gets crazy pulling the plug on it might not be enought to reset it properly if BOR is turned off. The pic will continue runing on the charge in caps and power adapters. Pulling MCLR to GND will help :-)

Also make sure low voltage programming is turned off or if you use that function make sure that pin is controlled properly ( if 877A has that feature)

AND make sure you program is set up properly for the 877A. You can not run the same program on a 877 as an 877A without getting problems :-)

One time is a freak accident.... 2 times is a bad habit