Timewarp not working?

Something happened within the last month or so that has brought some serious jutter with it.
When I load up my game, it's ok for the first few seconds, nice and smooth, then suddenly, it's as if timewarp is turned off. When I move my head I see a double image, like a 1 frame motion blur.

I thought maybe it was something I added to the game effecting performance, so I loaded up an old build that I know ran smoothly. Still bad.
Tried opting out of beta and Rift Core 2. got an update to firmware and software.
Still bad.

I can only assume that something has happened with both versions of Home?

It's not just my game either.. I've loaded up some other things and I get the same issue. Most recently was The Wave.

My rig is an i7-4960x, GTX 980. Been running everything like a dream (as I said, up until recently)

I've heard a few other developers complain about this same issue. I'm at a loss now.

Is this a known issue with a recent driver or firmware update?
Let me know.
Cheers