Wireless between Win98 and XP

Hello,

I am having the following problem:

I setup an ad'hoc wireless connection between a Win98 and an XP.
After booting the XP machine,the problem is that I can't ping the Win98, or
access file on it.

The connection only starts working between these 2 PCs after doing a ping
from the
Win98 machine to the XP machine.
After doing that, everything works fine, but the very first connection has
to be
initiated from Win98.

This does not occur at all between the Win98 and another Win98 machine I
have.
This behavior is systematic.

I suspect some setup to do on XP ??

Thanks for helping,
Regards,

Luc Lecocq