Stop using registry optimizers and cleaners. They do more harm than good, believe me.
Does the application have a restore function to reverse what it just wiped out? If so try that.
If not then you will have to do the following assuming we are talking Consumer (home) product versions here, these instructions do not apply to any Business/Enterprise versions:
1. Enable Windows Firewall. Uninstall all McAfee programs through "Add or Remove Programs" in Windows "Control Panel".
2. Use the MCPR tool, see this article: How to remove supported McAfee consumer products using the McAfee Consumer Products Removal tool (MCPR.exe). This will remove all McAfee remnants from your computer. (You must have Windows 7, Vista, XP or 2000, SP4 to use this tool)
3. Launch Windows Explorer and delete all McAfee files in "Program Files" but especially in "C:\Document and Settings\<user>\Application Data" and "C:\Document and Settings\All Users\Application Data". You have to set Windows Explorer to show all hidden files and folders (Tools > Folder Options > View tab). Just delete the McAfee folders even if they are empty in all the "Application Data" folders. Can be more than one!
In Vista: C:\Program Files, C:\ProgramData and C:\Users\yourname\AppData\Roaming
If you can't find these files don't worry. It just means that MCPR has done its job.
4. Reboot and redownload/reinstall your McAfee products directly from your account at the McAfee web site.
This issue can occur when information for MCSHLLPS.DLL has been modified in the registry. The changes to the registration information appear to occur after installation, as the installation and update have completed successfully. Please follow the below steps before trying to unistall and reinstall and see if this opens the security center.
1.Close any open McAfee SecurityCenter windows.
2. Run the attached fix_shell.bat file and wait for 2-3 minutes.
A command prompt window will display briefly followed by a dialog that states DllRegisterserver succeeded in mcshllps.dll.
3. Click OK.
Do report back if any issues.