In a recent update to cPanel, AJAX scripting was implemented to make menus "slide" and "expand", unfortunately this can cause problems for some users!
The error normally says:
"AJAX Failure! I failed 3 times. Please refresh the page and try again."
At this time we are only aware of this affecting Safari 4 users.
There are a variety of "fixes" on the internet available for this issues, many involve changing the WebKit on your computer, as we do not support customers own machines we recommend trying another browser before embarking on this type of fix.