This may be a question for the ArcGIS Server team (not JS API) but I'll ask it here anyway.There seems to be a problem with the gray basemap at the moment. I'm getting loads of NetworkError: 404 Not Found - http://server.arcgisonline.com/ArcGIS/rest/services/Canvas/World_Light_Gray_Reference/MapServer/tile...
messages. You can reproduce this using the sandbox sample http://developers.arcgis.com/en/javascript/sandbox/sandbox.html?sample=map_simple with options:
map = new Map("map", {
basemap: "gray",
zoom: 1
});