This seems to have started only recently, but every time I attach a USB device or removable media (SD Card) to my MacBook Pro running OS X 10.8.3 the mouse cursor freezes for a few seconds. The screen is still updating. It seems to happen right when the OS sees the external drive (via phone, camera, SD card, etc.)
I don't see a spike in CPU or anything else suspect, just that the trackpad stops responding momentarily. What would cause this and is there a way to fix it?