Windows 7 Network problems between Windows 7 and XP

[MBaeten]

Hi,
I have 2 pc's in a netwerk and a SMC router (4 ports and Wireless)
Both computers are connected to the Router with cable and wireless.
From Both computers I can acces the internet (Router is also gateway)
So I have 4 IP-adresses:
- XP 192.168.200.100 (wireless)
- XP 192.168.200.103 (LAN)
- W7 192.168.200.101 (Wireless)
- W7 192.168.200.102 (LAN)

When I do a ping from the XP pc to the windows 7 PC (..101 or 102) I get a reply from the network adapter of the WIndows 7.
But when I do the same on the Windows 7 PC to the XP pc (..100 or 103) I don't get a reply.
Why ??