The upload protocol changes between versions..
find the boards.txt file for the one that would upload (its just text)
and find the new boards.txt file in the new arduino
make the upload setting the same as the old file
eg
it will look something like
atmega1284p.upload.protocol=arduino
atmega1284p.upload.speed=115200
you need to find the correct protocol and upload speed for your bootloader
NB you need to restart the arduino ide if you change a boards.txt file to make it re load it
find the boards.txt file for the one that would upload (its just text)
and find the new boards.txt file in the new arduino
make the upload setting the same as the old file
eg
it will look something like
atmega1284p.upload.protocol=arduino
atmega1284p.upload.speed=115200
you need to find the correct protocol and upload speed for your bootloader
NB you need to restart the arduino ide if you change a boards.txt file to make it re load it