Error when applying Lens Blur

I'm having this issue too.  I have never been able to use the lens blur feature because of it.  I'm hoping to find a fix.  There are several of the newer features that just won't work on my system.  It's a fairly new computer and has the required specs.  It's so frustrating.  I also end up having to restart Lightroom any time I try to use a feature that gives me an error message because it stops showing me my progress in real time.  Like, if I apply an adjustment, it will show in the thumbnail, but not on the developer screen so I can see what I'm doing.

First up, that use of HDR Treatment. Is your Monitor specs up to the task? I think not based on all that red in the HDR side of the Histogram. Try without HDR Treatment.

Second up, what does LrC say about your GPU? What is shown in /preferences/performance?