replication merge not put instantaneous time out

replication type merge
suscription two(a-b)
function suscription (a)
not function suscription (b)
What this is the problem !! Help
error: replication merge not put instantaneous time out
thanks!
Christian,
please can you post up the complete error text from the merge agent, and
also list any distinctions between subscriber a and b.
TIA,
Paul Ibison