V! configuration error when writing

Hi. I am trying to program some 16F84A/04P. I have loaded the same program into these chips before but now I get an error message part way through programming. It says “Error Config-w wrote 0015 read 3FF5”.
I can confirm that the display shows the config word to be 0015.
The code was written by someone else and is code protected (I do have his permission to use it). I’m pretty sure I had this problem once before and overcame it with the program settings but can’t find what to do now. Can you help me please. The software I am using is REV 2.6.0

It sounds like you’re using the Progpic2 software. You can try speeding up or slowing down the speed, under Options. I believe high speed is more reliable.

You could also try the other software package that came with the kit, PicProg2009, or WINPIC.

Yes, you are exactly right. I am using quite a slow and very old laptop for the RS232 port but did not think to write more quickly, I actually slowed it down thinking that would be more accurate.
More to the point I did install PicPro2009 and have programmed some chips without the error although, at present I have been unable to test the chips out as the circuit boards are still being built but I am confident they will be OK now.
Thanks for your help and also the correct diagnosis of my problem.