ad-hoc network not connecting after reboot

i have 2 computers
1 PC with windowsXP pro SP2, which is connected to a router with a cable.
1 laptop with XP pro sp3(i've had the problem too with vista home premium
and XP sp2) connected via wireless from an ad-hoc network with my PC

the problem is, if i turn off both computers and turn them back on my laptop
can no longer connect to the network.
it is set to automaticaly connect but it doesn't
if i manually connect i see the connecting screen for 5 minutes at 1%, and
then it disappears and refreshes the wireless network list without being
connected.
my PC has no problems connecting.

the only way to get my laptop to connect to the ad-hoc network again is by
setting up a new ad-hoc network on both my PC and my laptop.