Hello,

Using your compiling line, I get an "reference to undefined global 'Unix'",
I've added "unix.cma" / "unix.cmxa" right before the -thread and it
then compiled just fine, and my dummy program worked. (if this still
doesn't work, mind sending everything make outputs ?)

Anyway, I don't know if you actually need all of the libraries the
book makes you load - I've only used "unix.cma -thread threads.cma"
and it worked just fine the couple of times I've used threads (change
.cma to .cmxa for ocamlopt)

Good luck,
Martinet Dominique.