Anybody seen this bug before? (Bokeh/DDOF)

[SleeperService]

http://i.imgur.com/QcAJwQJ.jpg

The above picture shows the problem. My DDOF/Bokeh will stop focussing correctly, and will instead freeze occasionally. You can see this most clearly in the small field of mushrooms - notice how there is a discontinuity in the focussing effect.

Has anybody else encountered this bug? I never used to, and I've come back to playing Skyrim after a few months, and now I'm seeing it several times a session.

Before anybody asks, yes I am using SLi, and I know there is no official support for SLi. I just wanted to know if someone with a single card has seen something like this before.

[ENBSeries]

Don't waste your time, SLI dof do not work.