Has your subscription already expired? Maybe that's why you are having the issue. I am only speculating of course. If you still have an active subscription try to uninstall and reinstall your software and be sure to use the MCPR removal tool and then download and reinstall the software. I will be right back with some info concerning this procedure.
How to uninstall or reinstall supported McAfee products using the Consumer Products Removal tool (MCPR) should get you back up and running. I might also ask that you be sure you are up to date with all Microsoft updates and your browsers are up to date even if you don't use IE as McAfee relies on IE to function.
Let us know if this resolves your issue
If by any chance you have Google Desktop installed, uninstall it via Control Panel > Programs, that is often the cause of this error.
This message has been reported many times here, and I looked into what it means when replying to a post in an earlier thread. The relevant parts of the message here are File A ("mscjsres.dll") and File B ("alert.html"). A is trying to do something with B and fails. If you look in the Event Logs you will find one or more messages with an Event ID of 12005 which attempt to explain what's happened :"InternetCrackUrl failed for (....)" - so it can't break down that string into its component parts. See https://community.mcafee.com/message/306812#306812 and following posts for more on this.
As to what causes it and how to fix it : I still don't know for sure, but if by chance you have Google Desktop installed, uninstall it (that worked for one person, or so he said). It could be malware interfering with McAfee, but it's possible that something has modified your Internet Explorer settings, and doing a browser reset might fix the problem.