how to fix error code -54

In what context?

== Error -54 ==

From an OS9 reference, error -54 is a software lock on a file or a permissions error. (Some of the old codes still apply to OSX although there is no formal list of OSX error codes.)

iTunes Library cannot be saved (Error -54) - https://discussions.apple.com/thread/1912814

Unknown error (-54) while syncing ipod - https://discussions.apple.com/thread/1082953 - problem was locked files

Why does iTunes keep showing a -54 error when I sync my iPad? - https://discussions.apple.com/thread/3727114

Error -54 possibly related to Touch Copy - https://discussions.apple.com/thread/3727114 - cleared by deleting preferences on iPad.