Graphics problem in Firefox (pic attached)
Why are there problems with progress bars? All other graphics seem to be fine.
Is this the same for all Firefox users?
It's not the same for everyone, but there have been some discussions in the troubleshooting section. Duolingo is aware of the problem so we'll just have to wait for a fix.
Edit - you actually posted one of those discussions; I guess you're asking for an update on the issue :)