For quite some time I've been seeing pages gray-barred that could be said to be of low quality for one reason or another. What troubles me is that, like g1smd mentions, some of them are important navigational pages. On some of these menu pages, I tried adding some verbiage just to have some indexable content to balance out the links, but no success so far. It's hard to know what Google is up to. It could be a signal that they don't want these pages in the SERPs, but the pages still pass PageRank to the destination pages.