The Pittsburg runningback from the late 80's is the last one I remember in recent history.  Of course, the Fullback position his chocked full of white land masses.  Though, I can't think of a single instant in the HB/FB role where there's someone of a different race "that could be doing it better" than the player that was selected.
I don't think "race" issues had anything to do with the overall numbers funkypants.  It had to do with the difference between the % at the player levels vs the % at the management/leadership levels.  The NFL is working to "correct" this.
Seems 50% of the starting QBs are black this year... can't say I ever rember that happening.  Too bad most of them suck and provide fuel for Rush Limbaugh's comments.  Of course, most of the white quartebacks suck this year too.
MiniD