I've spent days researching this problem and have found no solutions. I plug the Microsoft wireless mobile mouse 3500 transceiver into my USB 2.0 port and the cursor movements are so erratic that the mouse is useless. I try to use a Microsoft wired mouse connected to the USB 2.0 port and it does not work at all. However, both the wireless mobile mouse and wired mouse work perfectly when plugged into one of the two USB 3.0 ports. This problem occurs on my Dell XPS 17 L702X laptop, which is less than three weeks old. The laptop is running Win 7 Ultimate x64. I have installed the latest drivers from Microsoft's website. I have uninstalled them and reinstalled them but the problem remains. I have exchanged the Microsoft wireless mobile mouse 3500 for a new one but the identical problem remains. I do not have this problem on my Dell Studio XPS 7100, which is also running Win 7 Ultimate x64. The same mice that fail to work properly on the laptop's USB 2.0 port work perfectly with the USB 2.0 ports on the desktop. Everything in Device Manager (laptop) is up to snuff and no problems are indicated. Thank you in advance for your time and any assistance provided. C.B.