Maya 2015 and 3.3.2 Keyframe constraint on/off not working

Has anyone been able to get this to work or have a workaround? I’m trying to turn a constraint off at a particular point in the timeline. However it just stays locked at whatever is the first frame of the simullation. I want to start with it on, then turn it off, at say frame 300. But It stays on regardless of the keyframe value.

I have the same problem and i’m in maya 2014

Is this using the latest Maya plugin? Which version are you using?