I've posted an issue I had with netclient's META.in file:
http://sourceforge.net/mailarchive/message.php?msg_name=49AAFDA6.1030208%40citycable.ch
In the toplevel,
#use "topfind";;
#thread;;
#require "netclient";;
does not work.
But doing #require "netsys" and then #require "netclient" works out fine.
Replacing netclient's META.in by
version = "@VERSION@"
requires = "netsys,equeue,netstring"
requires(mt) = "netsys,equeue,netstring,threads"
archive(byte) = "netclient.cma"
archive(native) = "netclient.cmxa"
archive(mt,byte) = "netclient.cma http_client_mt.cmo"
archive(mt,native) = "netclient.cmxa http_client_mt.cmx"
solves my problem with netclient and multi-threading.
Cannot reproduce this with the current version.