I have the same problem on two PC's One with Win 7 Home Premium and one on Win 7 Ultimate.
It's probably best to list the commonalities you have between the two computers (and the same goes to the OP), as there's a couple of posters with multiple computers exhibiting the same issue, but a myriad of other posters saying no problems at all. Nobody so far (that i've noticed) has said "I don't have a problem with one of my machines but I do with the other"
Hence my suspicion would lie with a common 3rd-party app/add-in/piece of storage hardware.