I get the error, XDave - I usually exit HDRI-shop and then see if any HDRI or lightgen plugins are running in task man, close them, and start again. I tend to get the issue when I am using pure HDR files and not say generic .tif or .jpg files, so maybe you want to check your output? The sets in my freebie stuff are all TG with HDRI-lights, but I did add and remove some in order to fake radiosity. Looking at them now, I see I still have a ways to go ;-) 3D world gave away stitcher a few issues back - it's worth a peek if you want to try out other options than HDRI shop. ~S