Can ping to, but from from, Vista Home Premium machine

>Hi,
>
>just taken delivery of shiny new Vista Home Premium system.
>
>I have a simple home network, wireless router and a Win98 (yes, 98)
>machine, this new Vista box. The Win98 machine is wired to the router,
>the Vista machine is wireless.
>
>Between these two machines, networking fine, internet access fine etc.
>Both machines members of same Workgroup, IP addresses assigned by
>router using DHCP etc.
>
>I also have a work laptop, XP Pro, it is configured to work on home
>wireless LAN, DHCP, but it is not a member of the workgroup since it
>is a domain machine from work. But when in the home it can connect to
>internet etc.
>
>My problem is that I cannot setup even the most basic communication
>between the Vista machine and the XP laptop. Or in fact either of the
>workground machines adn the XP laptop, not that I cared before. (What
>has the Win98 machine ever done for me?)
>
>Vista machine IP is 192.168.10.3
>XP is 192.168.10.2
>Win98 is 192.168.10.4
>
>The Vista machine can ping and share files with the Win98 machine.
>The XP machine can ping either of the Win98 or Vista machines
>
>But neither of the Win98 or Vista machines can ping the XP machine,
>even though as far as I can tell their ipconfig setups are identical.
>I cannot connect to and FTP server running on the XP machine from
>either
>
>Firewall is disabled on Vista for test purposes, didn't make any
>difference though.
>
>Any ideas?