The latest on what's still a problem, what's getting fixed, and what's been taken care of, direct from the Blogger team.
Friday, April 30, 2010
Currently if your blog language setting is set to one of the Indic languages (Bengali, Malay, etc) then Adding a Gadget will return an error. As a workaround, you can temporarily change the blog language to a non-Indic language, add the gadget, and then revert to your original language setting.
The team is investigating this and we'll update this post once we have more information to share.