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[Reply #15 on:]

Im sorry, my mistake. It's on the FT232R chip. Pin 26.
I'v edited my previous post with this change.

[Reply #16 on:]

Im sorry, my mistake. It's on the FT232R chip. Pin 26.
I'v edited my previous post with this change.

That surely must be a mistake on the Nano's V3 schematic as the classic arduino Duemilanove uses the FTDI chip and shows pin 26 being grounded.
http://arduino.cc/en/uploads/Main/arduino-duemilanove-schematic.pdf

And from the FTDI datasheet, it says this about pin 26:

26 TEST Input
Puts the device into IC test mode. Must be tied to GND for normal
operation, otherwise the device will appear to fail.

http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf

Lefty

[Reply #17 on:]

I did see this solution (pin grounding) on another post http://arduino.cc/forum/index.php?topic=28280.0 but in my case I have I programmed my nano repeatedly for months and now all of a sudden I am getting this error on 2 different Nanos, using multiple different cables. If it was something wrong with the nano circuitry then why has it worked for so long?
I can get it working again by uninstalling the driver and plugging the device back in which I had to do on each usb port, but sometimes it will still not recognize and I have to go through the uninstall process again. Will keep you posted if I find anything.

[Reply #18 on:]

Typhoon, I had about 80 Nanos over the past few months. In last batch of 20, some "act funny" and seem to be recognized by Windows randomly while others are fine.
As I said before, I "sacrificed" on Nano and did the TEST-GND blob bridge and that fixed the random behavior - windows recognized it all the time after plugging in and out tens of times (repeatedly).

[Reply #19 on:]

Update:

Plugin the first time works on all 20pcs. If I plug in and out very fast (a few seconds in between), about 10 will not be recognized.
If I plug in and out with a delay of over 2 minutes, they all work... beats me.

[Reply #20 on:]

Ok you convinced me I will wire Test to GND, its going to be like performing heart surgery on those SMD pins.

[Reply #21 on:]

I was "afraid" to do it as well, but solder flows to the right place all on its own, so don't worry

[Reply #22 on:]

Another happy user which has fixed his Nano just a while ago. It should be written about the problem in capital letters on the official Arduino Nano page, and the schematics/boards updated.