Is is required for master and slave hosts to run the same version of 
slony? I guessing it probably is, but seems worthwhile checking for sure.

For instance the case under consideration is:

host1  Slony 1.2.10 Postgres 8.2
host2  Slony 1.2.15 Postgres 8.3

Due to the restrictions of package management (Debian system in this 
case) - to match the versions we'll have to roll our own Slony package!

regards

Mark