The error code is listed among a few in this Apple document:
Mac OS System Error Codes: 0 to -261
http://support.apple.com/kb/HT1618
This is the definition given there, for the Error code -50:
-50 (paramErr) Error in user parameter list.
If the folder you are trying to copy contains Mac OS X system
parts, user account info, or other items, there may be some
connection; but not necessarily.
This error can occur in several different (yet apparently similar)
actions involving file moving & copying, including using apps
intended on burning files to a disc. You could try repairing
the disk permissions on the computer's system using the
native Disk Utility and select the macintosh HD in the menu.
The above is not necessarily a fix for your specific circumstance,
since the error message can also appear while trying to sync an
iDisk or device data between the computer and some other item.
Sometimes, permissions on files or folders may have to be set
to 'ignore permissions on contents' or the equivalent, to copy
them from one place to another; this would depend on who
owns them in the computer, and if you are the Admin of it, etc.
You may have to further investigate this matter to see what ideas
involving your specific activities may invoke the error message.
I was able to find several instances where the same message
occurred while moving copying or trying to burn content, so to do
a search in google or in Apple Support may invite numerous hits.
Some of these would be irrelevant to your cause.
You could check the item's ownership using Get Info (highlight
single-click, and choose Get Info from File menu; or use Cmd
+ i, to bring up the info window on each item highlighted) to
see if something there may need to be unlocked or for the
purpose of copying, the permission level changed.
My suggestion is to read further, and if you have additional
information as to the content of the files or folders, that may
be helpful to any other readers who may have specific info.
In any event...
Good luck & happy computing! 🙂
