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?