<p>The Lightroom folder inside Application Support could have the wrong permissions preventing Lightroom from writing to it which can cause this error.</p>
<p > </p>
<ul>
<li>Navigate to the following folder: /Users/[user name]/Library/Application Support/Adobe/Lightroom</li>
<li>Highlight the Lightroom folder and chose File > Get Information</li>
<li>Under Sharing & Permission, verify that your have Read & Write Privileges. If not, click the padlock icon at the lower right, enter your password when prompted, then click the Read only entry and select Read & Write.</li>
</ul>