In a recent update, cPanel integrated AJAX scripting into the control panel. You may notice this in how menus "slide" and "expand," however it can cause browser incompatibilities.
The error appears similar to "AJAX Failure! I failed 3 times. Please refresh the page and try again." and it shows only in the email account section of cPanel. At this time it only affects Safari version 4.
This is a known problem with cPanel, they have a page about it here with a few ways to work around it, the below is copied from that page:
Problems with Safari 4
You can avoid these bugs either by clicking the click here link at the bottom of the page, or by running the latest version of WebKit, the HTML and CSS rendering engine used by Safari. Interacting with WebKit is the same as interacting with Safari.
Install the latest version of WebKit from http://nightly.webkit.org.
Enter Safari’s Preferences and set the default browser to WebKit.
We recommend removing Safari’s icon from your Dock to prevent accidentally accessing it in the future.
Add the WebKit icon to your dock or desktop.
An example of this icon can be seen in the figure below.
The WebKit Icon
The Email Accounts page is the only feature in cPanel known to be affected by the bug. It may also be important to note that Wordpress’ RTE requires the same fix.
In addition to these steps, connecting to cPanel's secure port (2083) also prevents this issue from occurring.