Since I upgraded my iMac i5 21.5" from OSX Lion to Mountain Lion, I've being facing problems by copying files from my HD to another drives. When I try to copy one or more files to my Time Capsule, or Flash Drive, or SD Card (for example) I frequently receive the message "Could not copy "xxxxxxx.xxx" file because it's being used." after insist some times, the file is transfered. This error is being more and more frequent each time. Curiously, this only happens when copying from my HD to another drive. Never had that copying to the same HD. I have other Macs runing M.L. and S.L. which are doing fine. The only machine that's giving this kind or error is this one. Any tip?
You may need to rebuild permissions on your old user account. To do this,boot to your Recovery partition (holding down the Command and R keys while booting) and open Terminal from the Utilities menu. In Terminal, type: 'resetpassword' (without the 's) and select the admin user. You are not going to reset your password. Click on the icon for your Macs hard drive at the top. From the drop down below it select the user account which is having issues. At the bottom of the window, you'll see an area labeled Restore Home Directory Permissions and ACLs. Click the reset button there. The process takes a few minutes. When complete, restart.