Can't upload my sketch from arduino IDE
Arduino IDEs v.1.6.x have recently been causing such kind of trouble on windows and mac systems. These problems seem to be caused by Java issues. Arduino IDE comes with java suit for it to work, installing java separately will cause problems. I suggest you uninstall java completely(by that i mean even the residue files that are not removed after uninstalling. For removing java completely you can use third party java remover like JavaRa ( https://singularlabs.com/software/javara/ ).
After doing so you can install the IDE again (i suggest to use .zip download of the IDE). 
If it does'nt help it check this out http://forum.arduino.cc/index.php?topic=341144.0
its possible that problem is caused by out dated executables after updating the IDE.

Hope it helps.