XP Home wi-fi to XP Pro

I have 4 computers. 2 are linked through a router to each other using wi-fi
and 2 are linked through a hub to this computer which is set up for ICS for
those two out through the wi-fi attached to this computer. This one uses XP
Pro SP2 and the other linked wi-fi uses XP Home SP2.

Until a week ago, both XP machines were using Home and talking to each other
quite OK. I decided this one was playing up a bit so reformatted and had an
XP Pro I had bought awaiting that event so put it in fresh. I set up
everything here and could see the XP Home and send data to it and copy from
it. I went down to the other machine and tried to talk to this one and it
wouldn't work. So, I came back to this and it still worked fine.

So what is it I am doing wrong? I can get this XP Pro to talk to the XP home
wirelessly through the router but not back the other way. I use only TCP/IP
and have manually assigned 10.1.1.x numbers and also currently have it using
the DHCP on the router and the situation is exactly the same. Meantime the
two Win98SE machines connected through the wired hub to this machine work
perfectly with the XP Pro machine either direction. Got me beat why Home and
Pro don't get on here.

Any help appreciated. Thanks.