Hi
Had some problem with IR refreshing in some scenes and found now that the problem connected with Ivy objects created with Guruware's Turbo Ivy plugin. If this object is visible in viewport IR restarts with any action such as panning, zooming, etc. with viewports which are not supposed to be rendered. It's doesn't matter is this object renderable or not. But if Ivy object is hidden and still renderable using Render hidden geometry, IR works normally. You can check example scene attached here.
Also problem can be solved by converting Ivy objects to poly, but it's not always useful