Roll Call offers this must-read report ($). It quotes an anonymous source as follows:

Another individual familiar with the study, who requested not to be named, said the commission’s unanimous decision not to adopt the Rutgers study had little to do with the study’s science. The EAC simply is having buyer’s remorse for a lightly managed project involving a sensitive subject that is being forced into a politically charged environment.
“This is a bipartisan commission and I suspect this was simply too hot to handle — especially with regards to the Republicans on the commission,” the source said. “If what they were looking for was a different kind of study, the EAC should have been clearer up front on what it wanted.”

I agree completely with this source. While this person did not want to go on record criticizing the EAC, my own post on this issue goes on the record: Is The EAC Being Appropriately Cautious or Cowardly on Voter Identification Research?. I expand on that criticism here.