Ubuntu – SSH Connection Error : No route to host

There are three machines in this scenario:

• Desktop A : user@1.23.x.x
• Laptop A : user@1.23.y.y
• Machine B : user@192.168.z.z

All the machines have Ubuntu 11.04 (Desktop A is a 64bit one) and have both openssh-server and openssh-client.

Now when I try to connect Desktop A to Laptop A or vice-versa by ssh user@1.23.y.y I get an error as

port 22: No route to host

in both the cases.

I own both the machines, now if I try same commands from my friend's machine, i.e. via Desktop B, I can access both my Laptop and Desktop. But if I try to access Desktop B from my Laptop or by Desktop I get

port 22: Connection timed out

I even tried changing ssh port no. in ssh_config file but no success.

Note: that 'Laptop A' uses WiFi connection while 'Machine A' uses Ethernet Connection and 'Machine B' is on an entirely different network.

Laptop A && Desktop A -> Router/Nano_Rcvr provided to me by ISP. So to one Router two Machines are connected and can be accessed at the same time.
here is my ifconfig output for both the machines :-
Laptop

wlan0

Link encap:Ethernet  HWaddr X:X:X:X:00:bc  
inet addr:1.23.73.111  Bcast:1.23.95.255  Mask:255.255.224.0
inet6 addr: fe80::219:e3ff:fe04:bc/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:108409 errors:0 dropped:0 overruns:0 frame:0
TX packets:82523 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000 
RX bytes:44974080 (44.9 MB)  TX bytes:22973031 (22.9 MB)

Desktop

eth0

Link encap:Ethernet  HWaddr X:X:X:X:c5:78  
inet addr:1.23.68.209  Bcast:1.23.95.255  Mask:255.255.224.0
inet6 addr: fe80::227:eff:fe04:c578/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:10380 errors:0 dropped:0 overruns:0 frame:0
TX packets:4509 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000 
RX bytes:1790366 (1.7 MB)  TX bytes:852877 (852.8 KB)
Interrupt:43 Base address:0x2000