That error suggests that there wasn't enough memory available. Did you make any changes to your PostgreSQL configuration? Do you get the same error if you reboot and then run housekeeping again?
Please enable logging in PT3 and then reboot and try housekeeping again. If you still get the same error attach the PokerTracker.log file to a Support Ticket so that we can see the full error message and more information about your system, which should help us see what is going on.