Has anyone had any wierd issues with these laptops and wireless access?

I have one here that's baffling me - if left alone for a while, the wireless appears to be working but actually ceases to receive any traffic. Still seems to be trying to send. The APs are old 3Com ones which are working fine for everyone else, no changes made to them recently firmware wise etc. The laptop still shows an association to the APs (which are unsecured so no WEP/WPA key issues) but nothing will send. A 'Repair' on the icon doesn't fix it, toggling the card on and off with the laptop key doesn't fix it; the only thing that seems to is a reboot. When the card is in the limbo state, any attempts to ping anything just show "Hardware Error" on the ping lines. Driving me a bit mad!