Recently while visiting a website I got infected by Live Security Platinum malware which disabled all security services on my PC. I was able to remove this using the free Malware Bytes Anti spyware tool. But the Windows firewall and McAfee firewall were unable to run due to some bugs made in the windows. As usual I started looking on Google for the solutions posted by others for similar problem. I found many proposed solutions mentioning issue in McAfee and re-installing it after clean removal. But none of them look promising to me.
Then today I landed on Microsoft Fix It Solution center. I came to know that Microsoft has already provided lots of automated tools to check and fix common problems in various windows version. When searched for my problem I landed on this page:
http://support.microsoft.com/kb/968002
You need to download small software pieces and execute them to check and fix your PC. And I am very thankful to them that this solved my problem. Hope this helps you too.