One more update. I was importing 77 folders, which I do about once every 3 months. Firefox just did the same thing. I think deleting the x-frame cookies allowed the folder list to display again.
I have had this same problem many times. It appears to be a browser related issue. I noticed it in Google Chrome tonight. After importing a dozen or so folders, the import fails but the importing progress bar starts and runs forever. However, after checking the “manage galleries” page, no gallery has been started. Clearing my chrome cache allowed the folder list to reappear. I figured this out after switching to Firefox and finding the folder list still worked in that browser despite not showing in chrome.
