Today I figure out a very useful tips for SE to Fix Category and Dropdowns Empty When Editing Profile in SE4. Occasionally, while using Internet Explorer, category and tab dropdowns are empty when creating or editing profile fields. This is caused by a bug in Mootools 1.2.x which reports DOM ready before theDOM is ready. This bug will be fixed in mootools v2.0.
To fix this problem, open the file./templates/admin_fields.tpl using a text editor. Around line 83, find the line of code that looks like this:
Change this line to:
This should now fix your problem. Hope next update of SE will fix it automatically.