If your web browser crashes when you open a page to edit, or contains large amounts of white space or in HTML mode contains lots of repeated invalid tags?
Unfortunately this is a bug in a 3rd party component, and although we have seen the result of the bug several times, we have been unable to repeat the cause of the issue, so have yet been unable to fix. The likely scenerio is that a user pasted in invalid HTML code and this crashed the TinyMCE editor component we use. TinyMCE is a 3rd party component, and we are dependent on their development team to ensure it is fixed.