I had some trouble uploading a sketch. The sketch would compile fine, but no matter the version of the arduino IDE, it would hang on the last part of the upload. I had to,
sudo killall avrdude_bin
Eventually, I found, after much googling, that ModemManager was causing problems. This can be disabled by,
systemctl disable ModemManager.service
After disabling ModemManager I've had no problems. Apparently you can add (excpetions).
Note: I'm running Ubuntu 15.04 (64-bit) and tried arduino IDEs 1.6.4, 1.6.5-r5, and 1.0.5 (Ubuntu repository)
Yes! I had the same problem.