When I want to add an image to a page or static block I use the media gallery and upload a new image.
Unfortunately, when I press the browse button I can select a file. But as soon as I select it, it freezes in all browsers I know the media uploader has been updated not to use flash anymore, which is a great improvement.
But It suddenly stopped working, and I am not sure how to debug this kind of problem using the inspector.
I have a small update; it appears to be a server-side issue. When I run the Magento install locally, it works fine, and also when I move the install to the server it freezes all browsers again!
Still not sure of what is causing this!