"ntpd unable to bind to wildcard address 0.0.0.0 - another process may be running"

This is because the ntpdate is running when you try to start the server. I haven't found reasons why to leave it installed so you could remove it if you are using ntp daemon:

sudo apt-get remove ntpdate

I've seen this on Debian Jessie. The cause appears to be a race between /etc/init.d/ntp and /etc/network/if-up.d/ntpdate, both of which appear to contain logic to lock each other out that doesn't actually work.

I like having the ntpdate command available even though I rarely use it, so rather than uninstall ntpdate altogether I've just inserted

exit 0

as the second line of /etc/network/if-up.d/ntpdate, which makes it do nothing. My ntp daemon now starts successfully at boot time.

Had a similar problem on Debian 5,

a simple restart of ntp solved it for me

/etc/init.d/ntp stop
/etc/init.d/ntp start

just in case other have same problem

NTPD was recently installed, it seems that a restart after install is needed, I noticed this on Debian 6 also.