Error copying files to an external drive

[ramuniz]

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 can’t 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!

 

[HappyJun]

Disk Utility from Utilities Folder

Hi, please try Disk Utility and verify the external drive for errors:

Connect your external drive.
Launch Disk Utility.
Choose the external drive from the sidebar (usually NOT the Macintosh HD).
Click First Aid tab.
Click Verify button (This will take for awhile, so be patient).
After checking and has errors, click Repair Disk.

You may also want to verify for permissions.

Warning: This may, or may not work. I'm not liable if something goes wrong or lost data.