dselect/apt: Error 550: not a plain file?

[Ed Cogburn <ecogburn@greene.xtn.net>]

	I'm using the dselect/apt/dpkg combo to download and install new
packages in potato from ftp.us.debian.org.  My system is already
slink/potato, from earlier downloads from potato.  Yesterday I
tried to download a large number of packages.  Some were
sucessfully downloaded, but a large number of packages were not
downloaded because dselect/apt said they were "not a plain file".
	I tried again today, but with identical results.  So does anybody
know what's causing this?  Is the problem with us.debian.org?  Has
anybody else using us.debian.org seen this?

TIA
-- 
Ed C.