Process **\MCSHIELD.EXE pid (428) contained unsigned or corrupted code and was blocked from performing a privileged operation with a McAfee driver.

In the McAfee forums, there are several posts similar such as:

https://community.mcafee.com/message/241542

I would pursue your issue out in their community since they already seem to know about it.

I would also suggest that, unless you are really fond of McAfee or you are being forced to use it, you consider replacing it with something that has a smaller footprint, uses fewer resources, and does not have these problems - something like Microsoft Security Essentials that you can get here:

http://windows.microsoft.com/en-us/windows/security-essentials-download

MSE supplemented with the free versions of MBAM and SAS should keep your running pretty clean unless you are a daredevil like me:

Download, install, update and do a quick scan with these free malware detection programs (not at the same time) and remove any threats:

Malwarebytes (MBAM):  http://www.malwarebytes.org/products/malwarebytes_free
SUPERAntiSpyware: (SAS):  http://www.superantispyware.com/

SAS will probably report a bunch of tracking cookies and you can just let it delete them.

Even if you keep McAfee, I would still supplement it with MBAM and SAS since no single AV program seems to know about everything.  If your McAfee says your system is clean, I would interpret that to mean - McAfee didn't find anything it knows about.  It is prudent to use more than one reputable scanner to get more coverage.

If you do choose to switch (and you can't have both at the same time), you need to be sure to use their uninstaller program that you can get from here:

http://service.mcafee.com/FAQDocument.aspx?lc=1033&id=TS101331

Your system will reward you with better performance.