My original post didn't appear on the list as downloaded, but one response indicates it made the list. Anyway, I found the reason for the buildworld failure as I was later unable to update ports, even pkg, with portmaster. Filesystem was corrupted, as evidenced by booting back to 10.1-STABLE amd64 and running fsck_ffs -y on the partition in question, not mounted. I kept getting errors on unreadable sectors, and it might have gone on forever had I not stopped it with Ctrl-C. Corrupted installation, 10-STABLE i386, was on a 32 GB Kingston Data Traveler USB 3.0. So all I can do is give up on this USB stick, it looks kaputt. End of story on this issue. Tom