In Windows Vista the networking components were designed to be much more intelligent and automatically adjust the network settings to optimize the connection speed. This is a great new feature. Your network components basically tweak themselves for optimal performance. In most situations, these components automatically adjust perfectly for best performance. However, with wireless WAN cards the detection of network conditions is flawed and can result in slower network performance.
To fix this problem, Microsoft has released a hotfix for users affected by this issue. If you have a Wireless WAN device, I suggest you give this hotfix a try. More »