I have installed the Arduino IDE per directions and all seems OK. I I open a sketch after starting the IDE using the desktop icon, and then do a compilation and upload, all works fine. However, if I start without the IDE being running, and merely double click the sketch file, the IDE starts, compilation proceeds with no error, but then I get an "upload error". Why is this?? Puzzling.
I previous post states that this is a bug in the IDE 1.6.10.
This bug has been reported to the Arduino developers(https://github.com/arduino/Arduino/issues/5173) and will be fixed in the next release. It may occur with any IDE version with Arduino AVR Boards 1.6.12(included with Arduino IDE 1.6.10) installed. The developer's explanation of the cause is:
Found it at last, avrdude-6.3-arduino2 had an unwanted dependency on libusb-0.dll . Launching the IDE by clicking the .ino bypasses the inclusion of IDE root in PATH, so the dll doesn't get loaded at runtime. Since that release of avrdude was quite unlucky we should revert to 6.0.1 in upcoming release, so this problem will be solved (and we must keep in mind to check for it before the next release).