Mac OS x 10.11 El Capitan crashes on Uploading

I see there have been a number of posts about difficulties with USB / serial connection via Mac OS El Capitan, and some suggestions to do with drivers (that should't be necessary), trying different versions of the IDE, and disabling kext signing in Recovery Mode.

What is curious is that whilst none of the fixes have worked for me, I notice that after booting or restarting the computer clicking on the Apple icon and then 'About this Mac' opens the usual window of info about the computer, but from the moment the IDE tries to upload a programme to a Uno R3, not only does that process never finish, but the 'About this Mac' doesn't work any more. No window opens.

This would suggest that there is something fairly fundamentally wrong with the way the uploader is working, interacting with a basic Mac OS process.

On another Mac, running Mac OS 10.7.5 Lion, there are no problems using the same IDE and board.

(MacBook Pro El Capitan / iMac Lion / a wide variety of IDE versions / Uno R3 Genuino)

Any explanations / ideas welcome.

I have the same problem and have spent some time downloading drivers and disabling SIP but still no luck. I can see the port and the upload starts but the Arduino IDE hangs. If I close or force quit the IDE I cannot then see the port again unless I restart the Mac. This is frustrating as I am in the middle of a project and need to complete it asap.

I have the same problem. I have a MacBook Pro 2007 with OS X El Capitain, and when I make upload the IDE returns the "avrdude: stk500v2_ReceiveMessage(): timeout" error and freezes, and nothing more happens. The IDE detects the board and everything, but does not ends the upload.

If I test the same code on a recent MacBook Air also with the OS X El Capitain, all works fine.

Do anyone have already resolve that kind of problem? Do anyone knows the steps to resolve this problem?

Thanks to all.