My scene:
1) NEW
2) Add Prop > Box
3) go to frame 100
4) Set VISUAL > Post Effect/LUT > I loaded in the "Blur" effect, to 100 (max amount)



Okay, everything works fine, it animates from 0 blur to 100, on frame 100. 
But if try to delete the key from the timeline, the options are grayed out.  Not sure if something is new/changed with timeline, or how it works to cut / delete. 
If I adjusted, say the IBL to a different amount, I can right-click to delete that key.  But this Post Effect Key can't be deleted from timeline.

Not sure how works, thanks!