Q: Can't write on disk, gives error code -50

What kind of drive is it?  A spinning (mechanical) hard drive?  You may want to run disk utility to check it.

Also, do you have a current backup?  If you don't, you may want to make sure your backups are up to date.

The next time you have the problem, note the exact time: hour, minute, second.

If you have more than one user account, these instructions must be carried out as an administrator.

Launch the Console application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Console in the icon grid.

Make sure the title of the Console window is All Messages. If it isn't, select All Messages from the SYSTEM LOG QUERIES menu on the left.

Scroll back in the log to the time you noted above. Select any messages timestamped then. Copy them (command-C) to the Clipboard. Paste (command-V) into a reply to this message.

When posting a log extract, be selective. In most cases, a few dozen lines are more than enough.

Please do not indiscriminately dump thousands of lines from the log into this discussion.

Important: Some private information, such as your name, may appear in the log. Anonymize before posting.

Also, launch the Terminal application in the same way you launched Console. In the Terminal window, type the word "mount" (without the quotes) and press return. Post any lines of output that appear below what you entered.

Do you have the hardware test built in to your computer? That would be my next spot along with what Linc has requested above. The disk utility's hard drive test is pretty crappy, its really just checking the OS, the scan it does on the actual drive is really brief.

If you do have the hardware test, I would try that. It would give you a good idea on the hard drive. Start computer up and immediately hold the D key.

http://support.apple.com/kb/HT1509

Also, how long does it take for this to occur? If fairly quick, you could try a safeboot and see if theres some sort of application thats hanging the OS up. Its a stretch but will give us a good idea of where to go from here.

When the problem happens, are you able to write to any external hard drives attached to the system? If the problem happens regularly, does its prevalence reduce if you boot the system into Safe Mode (hold the Shift key at startup)?

I have this problem too. I thought my HDD is broken, because this problem started after my Mac fell from my bed on the floor. I replaced HDD with brand new SSD and reinstalled system copletely (clean copy of OS X El Capitan), problem persists. I reinstalled OS X like 10x, still the same. I ran the disk utility, no problems found. Seems like some HW problem.

Please help.

Thank you.

John

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Macbook Pro 13,3" Mid-2009

4 GB RAM

240 GB Kingston SSD / 750 GB HDD

OS X El Capitan

When exactly does this problem happen?

Any Network drives involved?