Didn't read all 20 pages of posts, but here's the work around I've been using since this happened. Open two browser windows of simtropolis before logging in. Log in to the first browser window and search/find what you're wanting to download but don't click for the pop-up. Switch to the second browser window. Hit refresh. On refresh you'll be logged in. Now logout in this window. Go back to the first browser window. Click the pop-up link for what you want to download or look at. The pop-up will prompt you to log in. Log in and the pop-up displays normally and allows you to download. Continue browsing with the first window until you find something else to download and then do the same thing again in the second window. It's pretty quick for me using alt-tab and ctrl-c for my password or user name.
