Well, I still can't reproduce you problems.
Let's do the following:
1. Please, upgrade ORBit for latest version. I use 2.10 and probably, your bug is already fixed there.
2. Let's reproduce you problem with your modification of echo-client-t.c from ORBit's test, since your first test is uncomplete (there is no server and I don't know what etk_ functions are doing). So, let's use echo-client-t.c for test (If problem is reproduced with new ORBit). Of course, modify it with echo_client_thread (NULL) as in your last mail.
3. After all, try to attach with gdb (do gdb --pid=pid)to process which hands up and do such commands:
a) info threads.
b) for every thread do backtrace with two gdb command (thread <number> then backtrace).
Let's see there results.
Shmyrev.