Well, it's definatly not Have Blue, but it looks vaery much like an F-117 to me. And it is at the Skunk Works, so maybe it's an F-117 with experimental body mods...
Could it be one of the Full Scale Development (FSD) aircraft located 410th Test and Evaluation Squadron at the Skunk Works. There is mention that at least one of them was painted gray for a while (middle of the page):
More info: There has been two F-117 with light gray paint because of evaluation of best paint scheme for 24h operations (initially Nighthawk was used only in night-time operations). They were named Grey Dragon I (79-10783) & II (85-10835). The first one had two-tone and the second one had single tone paint scheme.
There was an article about the retirement of Grey Dragon II in Air Forces Monthly Nov 2006 issue:
On closer examination the two main differences I fins are the shape of the cockpit and the engine exhausts. There are two splines coming down off of the cockpit towards the rear and perhaps a raised area behind the cockpit.
http://www.f-117a.com/Senior.html
There was an article about the retirement of Grey Dragon II in Air Forces Monthly Nov 2006 issue:
http://shop.keypublishing.com/acatalog/afm_November_2006.html#a1148
Another angle here:
http://maps.live.com/default.aspx?v=2&FORM=LMLTCP&cp=ps31f954s2pt&style=o&lvl=2&tilt=-90&dir=0&alt=-1000&phx=0&phy=0&phscl=1&scene=6424680&encType=1
http://maps.live.com/default.aspx?v=2&FORM=LMLTCP&cp=ps315654s2md&style=o&lvl=2&tilt=-90&dir=0&alt=-1000&scene=6424665&phx=0&phy=0&phscl=1&encType=1