TeamSpeak Classic can't open the compressor codec. It is probably not installed.
This is unusual because starting client version 1.04, the installer will install the needed codec for you.
Try uninstalling/installing TeamSpeak Classic again. For those who are interested:
The codec TeamSpeak Classic uses is "Lernout & Hauspie CELP 4.8 kbit/s".

Check first if others can connect to the server. Try to connect using an ip number.
Can you play online games like UT and Q3 from your computer? Maybe you are behind a firewall
that blocks udp traffic?

If you run into this problem, enable DirectX in output settings.
If that still does not work, try starting the game first, then TeamSpeak, after that..
Perhaps it is the time to buy a new Soundcard? Or install Soundcard drivers?

The standard adminpassword is "admin".
(Reason why on the time people was saying they got their servers hacked,
because they never bother to change the default password, or choosing a strong one)