I'm getting this too on signs and placed skulls as well as chests, but oddly only at certain viewing angles.
I'd like to mention that the @p still does not work with "/scoreboard players reset @p" in 13w05a. As this bug is also reported here and report is marked as Fixed, could this be looked into again.
Can confirm issue. Surprised this has not been assigned or up voted as it will break all adventure maps that require any right click action in close proximity to a block.