Just a quick question, what version of McAfee are you using?
Have you tried accessing McAfee Security Center through the program files? Start>all program>McAfee>Security center
There could be a number of reasons why the McAfee Security Center does not open:
1. Conflicting program
2. You are infected
3. Bad installation of McAfee
Try starting a Scan in Safe Mode/or Safe Mode with networking. Let it complete and restart.