Configuration MacBook Pro 15 inch, Mid 2012 OS X 10.8.5 2.6 Ghz Intel core i7 16 GB 1600 MHz DDR3 I have installed a portable Hard drive 500 GBy, MyPassport for Mac. Format Mac OS Extended (journaled), recently formatted. Immediately after formatting I could copy a lot of files from different locations, desktop or other drives, no problems. All files are generated on this MAC. After a few minutes I tried to copy a file and an error message appeared : "The operation cant be completed because an unexpected error occurred (error code -50)." I found a procedure at this blog that solved the problem. switch to Finder hold the "option" key on the keyboard Click on the "Go" menu Select "Library" (hidden if the option key is not down) locate the folder "Preferences" locate the file "com.apple.finder.plist" move said file to trash log out log in test to see if fixed Problem solved. I copied other files. But after a while I want to copy another file, the same error message. Can any of you help me Thanks!