In the project below, there is a font sprite with 94 very lightweight costumes and no scripts. When dragging it into the backpack, and from there into a new project, I first get “4 of 4 assets uploaded” (why 4?), then the project is trying to autosave but never finishes, so I have to quit the browser manually (Safari + Firefox, MacOS). The sprite itself and all its costumes correctly appear in the new project immediately after dragging it in from the backpack. Can anyone reproduce this problem? The names of the costumes are one character each, some of which are non-ASCII. Could this be part of the problem?

Link to project: http://beta.scratch.mit.edu/projects/10054142

Same with Chrome and IE9 on Windows Vista, so it seems a cross-platform issue.