Cross post from infopop forums:
I just upgraded from 6.11 to 6.2 last night, downloaded the .zip from the members area last night and did the upgrade according to directions.
I too have lost all historic PM's. Oddly enough, it appears the script overwrote the recipient field, M_Uid for all old PM's to a value of '1'. So the sql statement above really doesn't work for me.
I'm guessing the only way I can fix is to use my backup I created and find the proper M_Uid for each of the 3k + PM's ???? ouch.