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Macintosh Endnote X2 requires the latest OSX Endnote Patch - 30 MB
If you want to know more about this patch and how to deploy it, instructions are available on the Endnote support site. The notes refer to 'the Mac OS X Patcher file': this is the file downloaded from the link above.
and a Windows Tutorial which uses Media Player - 136MB. Note that the basic Endnote installation will put a text manual on your computer for reference.