I think I've gotten around this.  It seems it was my disk or the 
base.tgz file.  I tried copying the base.tgz file to another MacHFS 
volume (along with all the other sets I have) on an external SCSI 
drive.  Base.tgz could not be copied because of a disk error.  I 
presume the same error that was causing the premature eof.

I reformatted (again) my disk, put another copy of all the sets on and 
now it seems to be working.

Thanks for letting me add to your inbox.  heh.

-Greg