Unable to start IPR mode

[maxwood]

I think this issue might be scene related but I can't seem to start the IPR mode in the scene I'm working in. It works okay in a new scene with a box/light.

If I click the refresh interactive rendering button the framebuffer it tries to start (as shown in the messages window) but nothing actually happens. I've included the message window below. The scene renders fine when not using IPR, I can send the files if that helps - just let me know where.

[tashko.zashev]

A demo scene will definitely help us to find where the issue is. Please post it here or send to support@chaosgroup.com if there is any confidential data.
Thank you.