John Kerry's name appearing in the recent SHA256 checksums[0] might have spooked them, but it's entirely conjecture at this point.
[0] pre-commitment 1: John Kerry 4bb96075acadc3d80b5ac872874c3037a386f4f595fe99e687439aabd0219809
[0] pre-commitment 1: John Kerry 4bb96075acadc3d80b5ac872874c3037a386f4f595fe99e687439aabd0219809
pre-commitment 2: Ecuador eae5c9b064ed649ba468f0800abf8b56ae5cfe355b93b1ce90a1b92a48a9ab7
pre-commitment 3: UK FCO f33a6de5c627e3270ed3e02f62cd0c857467a780cf6123d2172d80d02a072f74
claim from intelAnon that Ecuador had caved in to pressure from the Clintons:
https://pbs.twimg.com/media/Cu7pNidVIAAUweO.jpg:large
The hashes then being a message from Assange, or it my be Assange being paranoid.. Or something else entirely.
[0] pre-commitment 3: UK FCO f33a6de5c627e3270ed3e02f62cd0c857467a780cf6123d2172d80d02a072f74