Correcting blank image and link dialogs in Joomla

I was going nuts! When I worked on my friend's Joomla site from home, the Image and Link dialogs appear just fine:


But when I tried it from work or when my friend did it from her house, the dialogs came up blank:


I tried every combination of browser setting and browser (Firefox, Opera, IE). Nothing. What was so magical about my machine at home?

I found the answer on Alex Le's blog. It turns out that my site home (as defined by $mosConfig_live_site) was set to www.site_name.com while I was firing up the administration console with http://site_name.com/administrator (notice the lack of www). Once I launched from http://www.site_name.com/administrator, the edit dialogs are dandy again, just like they are from home. Thanks, Alex!