Yeah, Korg product support was eventually able to help me out. To quote the email:
"Thank you for your inquiry regarding the nanoKONTROL. Do you use any other USB-MIDI devices with your computer? If so, you may have hit a built-in 10 device limit within the Windows registry. Look forward to hearing from you"
In a follow-up email, the support rep attached an article from EQ Magazine. Here is the article in its entirety; everything from here on is a direct quote from the article.
These operating systems can install a maximum of
ten MIDI device drivers; after that, they fall down and say
“no más!” And it’s not hard to use them up if you have
lots of devices. For example, if you install a USB MIDI
device driver while it’s plugged into one USB port, then
plug it into a different USB port and install the driver
again, you now have a duplicate driver and have used up
two MIDI device drivers. The same will happen if the
interface is on a PCI card, and you change its slot. The
solution: Go into the registry, hunt down duplicate driver
entries, and delete them.
RME has an excellent FAQ on this subject by Matthias
Carstens at
http://www.rmeaudio.
de/en_support_techinfo.php?page=content/support/e
n_support_faq_10entryd. However, it’s written more for
intermediate users, so we’ll deal with the issue on a more
basic level. Ready? Let’s fix it.
DEALING WITH THE REGISTRY
The Windows registry is a scary place for the neophyte, but
we won’t be doing anything too drastic. Still, it’s a good idea
to back up your registry in case you commit some egregious
error, as messing up the registry could screw up your
computer big-time (so don’t blame us). Refer to
Microsoft’s instructions for registry backup at
http://support.
microsoft.com/kb/322756/.
(Incidentally, if you don’t want to edit the registry,
M-Audio offers a “MIDI Fix” utility at
http://www.maudio.
com/index.php?do=support.drivers&k=driver&s=8
&o=Windows+XP&f=84. This clears out previouslyinstalled
MIDI devices, as described in a text file included
with the utility, but you will have to reinstall the deleted
drivers manually.)
1. Go Start > Run and type Regedit.
2. Locate the HKEY_LOCAL_MACHINE key and click on the
+ sign to its left to expand it.
3. Go down and open the tree as follows: Software >
Microsoft > Windows NT > Current Version.
4. Under Current Version, click on the Drivers32 key. A list
of sub-keys will show up in the right pane (Fig. 1); locate
the Midi sub-keys (Midi, Midi1, Midi2 . . . Midi9).
5. At this point, you have two options. Either one involves
deleting a MIDI sub-key by right-clicking on the key
name and choosing Delete. One option is to delete each
Midi sub-key (Midi – Midi9), thereby guaranteeing you’ve
deleted any duplicates, and re-install any necessary
device drivers from scratch. The other option is to verify
which keys are duplicates, and delete the duplicates. If
you delete a “wrong” driver key, worst case is that you’ll
need to re-install the driver for that device (if that forces
you to check the net for the latest drivers, that might
actually be a good thing!).
6. In Fig. 1, note how there are two entries for usbkt1x1.dll
(both are circled in red). To verify that these are duplicates,
type Ctrl+F to call up the Find function, and type
in (for example) usbkt1x1.dll. Keep hitting F3 to find all
occurrences of usbkt1x1.dll.
7. Once you get out of the Drivers32 key, you’ll find individual
instances where the drivers occur, with information in the
right pane (Fig. 2). This example shows that Midi6 represents
the driver for the M-Audio USB Keystation. However,
it turns out Midi1 also shows an M-Audio USB Keystation
driver with the same characteristics — clearly a duplicate.
8. After verifying the duplicate, return to the Drivers32 key
and delete either one of the duplicate sub-keys. You’ve
now freed up a MIDI device driver.
In my situation, after deleting two duplicates there was plenty
of room for the Yamaha Motif XS6, and all four of its ports
appeared. So next time you try to install a MIDI driver and
nothing shows up . . . check your registry!