McIlroy's tee shot on the par 3 #2 landed right next to, but not on, a plastic sprinkler head cover in the rough near the green. McDowell wanted relief, and he and Furyk got into it as to whether he should get relief. It delayed play by about 10 minutes or so -- the referee in the match called in the head referee to clarify whether relief should be granted. It wasn't, McDowell hit an indifferent chip, and Euro ended up losing the hole. And from the TV reports, the Ulster-men were pretty PO'd about the whole thing.
For what it's worth, when I saw the shot land, my immediate thought was: I wonder if Euro will ask for, and get, relief. McDowell argued it was a "50-50" situation, and argued he deserved the benefit of the doubt in getting relief. Furyk said it was more "80-20" against, and pretty much forced the ruling from the referees. On-course commentators suggested relief for the Euros would've given them an easier shot -- perhaps on the fringe of the green, vs. the rough.
Personally, I didn't think either side was out of line -- it was real close to whether the sprinkler head cover interfered with the stroke, and I didn't think McDowell was out of line to ask about relief. But I also don't think Furyk was out of line -- and he was pretty polite but firm about it -- in questioning the request.