I have repaired the disk permissions but can anyone suggest why is this happening?
The original RemoteDesktopMenu.nib was delivered by the package com.apple.MacOSX.lang.es. It was the old style nib (next interface builder), a directory containing a nib file. The package com.apple.pkg.RemoteDesktopClient delivered the nib file in the new format, a single Apple binary plist. Nothing to worry about.