clr_optimization belongs to .NET I believe and MPSSVC is Windows Security Center or part of it. McAfee software, like most 3rd party security software controls Windows Security once installed. Occasional errors or warnings are not unusual although I haven't seen that paticular one in the Event Viewer in my Windows 7 Ultimate SP1.
Run McAfee Virtual Technician to see if it finds and fixes anything: http://mvt.mcafee.com/
Assuming you have Win 7 totally up to date in all aspects and this issue bothers you, I would open a case with Technical Support. It's free by phone or online chat and linked under Useful Links at the top of this page.
They may be aware of an issue that I am not.
I looked further into this error. Why do you think McAfee has anything to do with .NET runtime optimization service? Also Windows Firewall is disabled when McAfee is installed so any errors pertaining to it can be ignored.
As long as the system is functioning properly and SecurityCenter (McAfee) says it is protecting, then you shouldn't worry about it.
As I stated earlier errors in Event Viewer are normal. I've yet to see a system not produce any.