Debian Etch packaging problem?

Regarding pgadmin3-data
File on mirror(s) = 2722978 bytes
Size in "Packages"/apt-cache show = 2722412

Obviously this causes an error:
Failed to fetch 

ftp://ftp2.uk.postgresql.org/sites/ftp.postgresql.org/pgadmin3/release/debian/dists/etch/pgadmin/binary-all/misc/pgadmin3-data_1.6.3-1~pgaoetch1_all.deb
Size mismatch
 
E: Unable to fetch some archives, maybe run apt-get update or try with 
--fix-missing?

Have checked a German mirror too, and confirmed it's not just UK#2 with 
that filesize.
I'm upgrading from 1.6.2-1~pgaoetch1 though I don't think it's relevant.

--   Richard Huxton  Archonet Ltd