Our company has Microsoft Engineers that assist in testing and development which work out of offices on occasion. They have Vista laptops with Intel 2915ABG chipsets. We currently support only B/G. We have a guest WLAN (non-broadcast SSID and open authentication/encryption) but because of latenct issues makes it unusable for them. They are seeing response time in excess of 1000 ms compared to company laptops of 30 ms.
My gut feeling is that there is some sort of driver issue but they state they have the lastest drivers from Intel. Has anyone seen this?
Check the quality of the link from the location where Vista laptops are located. Try improving the coverage or move it to a different location and check. Check if there are any firewall causing this by disabling them.
They may have the latest driver from their manufacturer, but they probably don't have the latest intel reference driver. The 2915abg isn't the worst intel chipset I've had experience with (that title goes to the 2200bg) but it's by far not the best (that title goes to the 3945... I haven't had the chance to mess with the .n chipset). All intel wireless chipsets seem to have issues that are resolved by the latest driver. I'd check out this site:
and see if there is a newer reference driver they can try. I've had similar experiences with any Intel Centrino based laptop (high latency, low signal, etc) that are *always* resolved by updating to the newest driver. Best of luck!