I've encountered this. Sorry for the bump thread, mods, I'm not sure if it's a forum faux pas, as I've not posted for well over a decade.
The MZ-N10 I bought new (about 2002 maybe), had this problem a few months after purchase. I sent it back under warranty to have it fixed, it came back, then after over a year of use the same thing happened, this time out of warranty. If I remember correctly MD recorder was sent back with the repair notes which stated the mainboard had been changed.
A few months ago I decided to dig out my MD recorders after frequenting r/minidisc on Reddit, and see if they worked. By some miracle the battery on the N10 still worked (as did the battery on my mint MZ-NH1), despite neither being used since 2006, so I have been playing around with them ever since. I am able to transfer music to my NH1 in NetMD mode, but can't with the same PC, driver, cabling to the N10, it briefly flashes PC--MD on the screen when unplugging cable, but that's all, that applies connecting directly to the unit or through the dock. So it's possible the chip that governs USB connectivity in my N10 is faulty; that's my take on it.