the other machine sees the Access Point along with my home router, as per iwlist scan:
[CODE]lo        Interface doesn't support scanning.

eth0      Interface doesn't support scanning.

wlan0     Scan completed :
          Cell 01 - Address: 00:24:89:5B:DA:6D
                    Channel:6
                    Frequency:2.437 GHz (Channel 6)
                    Quality=70/70  Signal level=-29 dBm
                    Encryption key:on
                    ESSID:"Vodafone-XXXXXXX"
                    Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s
                              24 Mb/s; 36 Mb/s; 54 Mb/s
                    Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 48 Mb/s
                    Mode:Master
                    Extra:tsf=000000329969718b
                    Extra: Last beacon: 430ms ago
                    IE: Unknown: 0011566F6461666F6E652D3131343336353733
                    IE: Unknown: 010882848B962430486C
                    IE: Unknown: 030106
                    IE: Unknown: 2A0100
                    IE: Unknown: 2F0100
                    IE: Unknown: 32040C121860
                    IE: Unknown: DD760050F204104A00011010440001021041000100103B0001031047001038BC60F2291E166EF52A8C241EF1A3111021000842726F6164636F6D1023000842726F6164636F6D1024000631323334353610420004313233341054000800060050F20400011011000A42726F6164636F6D4150100800020088
                    IE: Unknown: DD090010180203F4040000
                    IE: WPA Version 1
                        Group Cipher : TKIP
                        Pairwise Ciphers (2) : CCMP TKIP
                        Authentication Suites (1) : PSK
                    IE: Unknown: DD180050F2020101800003A4000027A4000042435E0062322F00
          Cell 02 - Address: 06:15:AF:67:7B:15
                    Channel:1
                    Frequency:2.412 GHz (Channel 1)
                    Quality=46/70  Signal level=-64 dBm
                    Encryption key:off
                    ESSID:"NegraModelo"
                    Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 6 Mb/s; 9 Mb/s
                              11 Mb/s; 12 Mb/s; 18 Mb/s
                    Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s
                    Mode:Master
                    Extra:tsf=0000000012b83182
                    Extra: Last beacon: 460ms ago
                    IE: Unknown: 000B4E656772614D6F64656C6F
                    IE: Unknown: 010882848B0C12961824
                    IE: Unknown: 030101
                    IE: Unknown: 07064E4149010B14
                    IE: Unknown: 200100
                    IE: Unknown: 2A0100
                    IE: Unknown: 32043048606C
                    IE: Unknown: DD180050F2020101880002A3400027A4000042435E0062322F00
                    IE: IEEE 802.11i/WPA2 Version 1
                        Group Cipher : TKIP
                        Pairwise Ciphers (2) : CCMP TKIP
                        Authentication Suites (2) : 802.1x PSK
                    IE: WPA Version 1
                        Group Cipher : TKIP
                        Pairwise Ciphers (2) : CCMP TKIP
                        Authentication Suites (2) : 802.1x PSK
                    IE: Unknown: DD0900037F01010020FF7F
[/CODE]

Now let's see what I got on my Access Point machine:
[CODE]~$ iwconfig
lo        no wireless extensions.

eth0      no wireless extensions.

wifi0     no wireless extensions.

ath0      IEEE 802.11g  ESSID:"NegraModelo"
          Mode:Master  Frequency:2.412 GHz  Access Point: 06:15:AF:67:7B:15
          Bit Rate:0 kb/s   Tx-Power:17 dBm   Sensitivity=1/1
          Retry:off   RTS thr:off   Fragment thr:off
          Power Management:off
          Link Quality=0/70  Signal level=-95 dBm  Noise level=-95 dBm
          Rx invalid nwid:5  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0[/CODE]

My /etc/network/interfaces file:
[CODE]# Set up the local loopback interface
auto lo
iface lo inet loopback

# Set up the external interface
#
# Don't forget to change eth0 to the proper name of the external
# interface if applicable.
#
auto eth0
iface eth0 inet dhcp

# Set up the internal wireless network
#
# Don't forget to change wlan0 to the proper name of the internal
# wireless network interface if applicable.
#
# If you would like to use WEP, uncomment the line 'wireless-key'
# and replace '<key goes here>' with a WEP key.
#
# You may also change the network essid and channel.
#
auto ath0
iface ath0 inet static
    wireless-mode master
    wireless-essid NegraModelo
    wireless-channel 2
   #wireless-key <key goes here>
    address 192.168.0.1
    network 192.168.0.0
    netmask 255.255.255.0
    broadcast 192.168.0.255
[/CODE]

[CODE]~$ ip route
192.168.1.0/26 dev eth0  proto kernel  scope link  src 192.168.1.8
192.168.0.0/24 dev ath0  proto kernel  scope link  src 192.168.0.1
169.254.0.0/16 dev eth0  scope link  metric 1000
default via 192.168.1.1 dev eth0  metric 100[/CODE]