First of all, the mentioned paths are on your Mac. "your mac"\Macintosh HD\Developer\Lazarus\...\
I used the trial&error approach actually to replace the files with newer versions. I just checked what were the changed files since beginning of March (release date of 2.6.4) and copied them over into the respective Lazarus folders.
I read somewhere that the use of InsertItem was changed, and that this was causing the problems. In the 4 files the new behavior was coded.
Hope this helps.