Problem in Customized

I'm currently running CAPro v1.1 on my four networked sites. I'm having a problem with the Appearance/Customize option. When I select Appearance/Customize, the CAPro menu appears on the left side of the window, but instead of rendering the web site image, the right side goes blank, and the clock icon appears (the rotataing dot in the circle) and stays that way for at least several minutes. (My patience runs out after a while, and I cancel out.) The menu itself appears to remain responsive (although I'm loathe to make any actual changes for fear of breaking something). The sites do not appear to be broken, just the editor.