UPDATE 2: We've noticed that both hard drives we've tried (small, portable external ones for traveling) have made clicking noises when mounted, so you can hear the drive spinning. Hubby suggested that might be a current problem? So, maybe it's trying to do a task like verify the entire contents of the drive before mounting, but because it's only USB powered it's chugging along not very quickly.

To test, I'm letting the second USB drive sit connected to the edge for a few solid minutes before giving up on it, to see whether it just takes that long.

As for the SD card reader not being recognized - could that have something to do with drivers? I know in an earlier thread it was stated (probably by boris!) that keyboards/mice have pretty generic drivers, so that's why we don't have problems with most of them. What about a USB card reader? Would that likely require a generic driver, or something more specific?