I have an Acer Travelmate 4600 running XP Pro with SP2. It connects to my wireless network which is configured to use WPA personal. I have tried both AES and TKIP. The machine is fully patched with windows update.
Some days it works perfectly and other days it loses connection 5 - 10 times a day. The signal is fine - the machine is 5 metres away with no obsctructions. When it loses connection it pops up a message about not being able to find the the correct certificate for the SSID. What is strange is that both the wireless network and the noetbook are set to use WPA personal. It is definitely the notebook because it happens on other WPA networks. WEP networks do not pose a problem.