A Sony Pictures representative has said it's down to getting the licensing all sorted out and "not specific to Xbox", though timing would suggest otherwise.
They say talks are underway with "relevant parties" to address the problems "related to the distribution of its motion pictures." It's ongoing so that's all they'll say on the matter.
Whether this is a genuine licensing issue or a clever little plot to put a fly in Microsoft's NXE ointment we'll never really know. The timing is a rather big coincidence.
"This issue is not specific to Xbox or any other individual platform," said the rep to MTV.
"Sony Pictures is currently in discussions with the relevant parties to resolve certain licensing matters related to the distribution of its motion pictures."
"Given the ongoing nature of these discussions, we don’t think it is appropriate to comment further at this time."
Source: VG247