I hate USB Hubs. Some people never have a problem. And for some, they never work. XP doesn't "require" you to disconnect a USB device through their software, but when you don't, they tend to break - in other words, fail to recognize devices. The easiest trick that I found that worked (and it does not always) is to power down the machine and then pull its electrical plug. Wait about an hour before plugging it back in and restarting the machine.