Window within a window

I’ve not had this type of problem in over four years of operating this system in this configuration. This is a new appearance of this anomaly with me.

I’m currently running CMS version 1.7.9, I’m accessing the CMS server using a MAC desktop. (both of these conditions have been the same for years) and while creating a new dataset, when “adding a column” to the dataset, I expect the popup window to appear. Instead, the response lags, then a duplicate window appears within the window I’m working in. (see attached)

I found this same reaction happens regardless of whether I’m using any of the following browsers: Safari, Firefox, or Chrome.

Popup windows are “allowed” in the browser, and other setting (to my knowledge) have not changed. Has anyone run into this and solved the problem?