I have seen this too but only on a virtual server. I moved the database to a similarly configured physical and didn't have the issue.
I have a case with MS that I will be working tomorrow on an issue with the virtual server and I will be addressing this issue so, I will certainly share with you what I find.
Until then though, I am clueless.
Haven't researched it much yet but probably should.
“He is no fool who gives what he cannot keep to gain that which he cannot lose” - Jim Elliot