I believe IME stands for input method editor, and allows you to use an alternate key mapping without the need for another input device. Helpful for people who need to type in multiple languages (where one is not based on western characters). IIRC, microsoft has IME's for Chinese, Korean, and Japanese on their download site.
I haven't answered your question (because I don't know what the toggleime function does for UT), but hopefully this will point you in the right direction.