Erratic CPU usage by mscorsvw.exe (.NET Runtime Optimisation Service)

mscorsvw is a process that pre-compiles .NET binaries. Your updates may have triggered this activity. At least, that's what http://blogs.msdn.com/b/davidnotario/archive/2005/04/27/412838.aspx says is happening.

You might get more clue what exactly is happening if you can run the sysinternals procmon utility. That will tell you what file(s) mscorsvw is hitting or focusing on, and help determine if it is actually focusing on potential .NET files.

From that website, if this is what's happening, running

ngen.exe executequeueditems

should "clear out the queue" by having it run everything at once instead of waiting for the CPU to become idle, as it appears is when this is happening on your server. Once it is done with the pre-compiling, it should stop happening.