Problem Insert/Edit Image in Visual mode 2.12

I upgraded to 2.1.2 but now when I write a new post in Visual mode and I click the Insert/Edit Image icon to insert an image then an empty window pops up. Because the window is empty (there aren’t any fields or texts or anything) I cannot instert an image. I can’t close the window that popped up either. The close-window-button is there at the top-right but it doesn’t work. The window sort of gets stuck to my mouse so it follows my mouse movements. I don’t know why this is happening.

I’m using FireFox (latest) and I also tried in Opera and in Opera basicaly the same thing happens.

I have 3 blogs, all 3 upgraded to 2.1.2 and I have this problem on two of the three blogs. What could be causing this? Perhaps a corrupt file that needs to be reuploaded?

Thanks.