I have the same problem. Didnt notice it for a while. I happened to clear the index because my HDD (which is SSD) was only registering 5.9 (this is because included in the index was my storage D drive). Fixed that ok but dropped my ATI 4890 to 6.0, which is silly when my other PC with a new 512mb 5670 in is scoring 7.0. By the way guys, it does matter what the WEI score is because thats what customers look at when buying. We know its fairly irrelevant but I'm afraid less well knowledgable peeps don't... thus MICROSOFT IF you are going to provide this benchmarking then please endeavour to get it to a relative scale and accurate!!
Its clearly an update gone wrong either from ATI or MS, possibly to allow some overhead for FERMI and the current crop of 5xxx series. Its hard to imagine a single 4890 getting 7.0 when 2 or 3 next gen cards in multi GPU set up can only obtain 7.9 max.