Can you see the feedback button on my.sprintr.com ? Are you using the Mendix App Store version? Maybe update it, if its outdated?
I just pulled the widget fresh from the Mendix App Store.
Oh, got it! Your question "do you see the feedback button" did it.
I'm sorry, I found the problem. I had a proxy setup in Firefox. I think Chrome used the Firefox settings until I tried IE. After that, Chrome suddenly started to work, maybe it switched to the IE proxy setting?
Anyway, thanks for the help!