[Serusers] ser & sems

Im running the latest ser with sems. Whenever I dial 958 I get the number reader announcement everytime. However when I dial an offline user or conference room, many times I dont get any speech. The call is connected but I just get silence. The server is on a public IP, so no nat issues. Firewall is correct, otherwise I wouldnt get the number reader working! All my fifo's are correct with the correct permissions etc, and my config file must be ok, as sometimes voicemail & conference announcements are played, sometimes not. Sems in debug mode displays this error everytime I get silence rather than the voicemail announcement- (4836) ERROR: stop (AmThread.cpp:99): pthread_detach failed with code EINVAL: thread already in detached state. Any ideas anyone?? Andy Thomas