Ubuntu – X over SSH to Ubuntu server

I'm trying to run X remotely from an Ubuntu server. I've installed gedit on the remote machine, and tried:

adam@laptop $ ssh -X adam@myserver
adam@myserver $ gedit
cannot open display: 
Run 'gedit --help' to see a full list of available command line options.

I've tried it with another program:

adam@myserver $ filezilla
Error: Unable to initialize gtk, is DISPLAY set properly?

Here's the SSH log, using ssh -X -v:

OpenSSH_5.3p1 Debian-3ubuntu5, OpenSSL 0.9.8k 25 Mar 2009
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to [Server ip and name omitted, Adam] port 22.
debug1: Connection established.
debug1: identity file /home/adam/.ssh/identity type -1
debug1: identity file /home/adam/.ssh/id_rsa type 1
debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-2048
debug1: Checking blacklist file /etc/ssh/blacklist.RSA-2048
debug1: identity file /home/adam/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_4.7p1 Debian-8ubuntu1.2
debug1: match: OpenSSH_4.7p1 Debian-8ubuntu1.2 pat OpenSSH_4*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3p1 Debian-3ubuntu5
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host [Server ip and name omitted, Adam] is known and matches the RSA host key.
debug1: Found key in /home/adam/.ssh/known_hosts:292
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Offering public key: /home/adam/.ssh/id_rsa
debug1: Server accepts key: pkalg ssh-rsa blen 277
debug1: Authentication succeeded (publickey).
debug1: channel 0: new [client-session]
debug1: Entering interactive session.
debug1: Requesting X11 forwarding with authentication spoofing.
debug1: Sending environment.
debug1: Sending env LANG = en_US.utf8
debug1: Remote: No xauth program; cannot forward with spoofing.
Linux sftp-waze 2.6.24-10-xen #1 SMP Tue Sep 8 19:06:53 UTC 2009 i686

Unfortunately, these programs have no verbosity flag, so that is all the information I have.

What's wrong? Is it even possible to run remote X on ubuntu server?