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Getting error -50 when copying data in OS X.
Some LaCie drives ship out formatted FAT32 so they will be ready to use on either a Mac or a PC. If you are getting error -50 when copying to a LaCie drive, or any drive formatted for PC, it is because of the following:
Certain characters that can be used in a Mac OS X filename are not allowed in MS-DOS filenames. This can prevent the file from being copied, and can occur when a filename contains non-printing ASCII characters, or any of these characters: ? / \ < > " | > *.
Either copy the data off of the drive and use Apple's Disk Utility to erase the drive in HFS+ format, or change the filenames of the documents that cannot be copied.