I’ve tried connecting the phone again, then doing a proper "Eject" on it before disconnecting the USB cable, but that didn’t help.
I’ve never had this problem before, but today, I started getting the "the device has either stopped responding or is disconnected" error. But it only shows up if my phone isn’t connected. It just pops up once in a while on its own. Things were working fine until today. Does anyone have any ideas about this? It looks like the message comes from something call SIhost, but that’s a system file, so I can’t just kill it.