I had the same problem in Windows 7, and it persists in Windows 8. This happened in three computers I had, including the current one.
I have configured three input languages, and I assign a hotkey (alt+shift+number) to each of them. However, after some time, the hotkeys are reset; sometimes it's just some of them, other times they all disappear. They often keep working, but there are
a few times when I can't switch languages in any other than pressing shift+alt or by clicking.
This issue may also be related - Sometimes I can't change languages from IME to English or any other. For that, I have to switch between input methods in IME (with alt+`), and only after I do that I can use the hotkeys. Again, switching languages with
shift+alt works, but the custom hotkeys don't.
Does anyone know the cause of the problems I described? Is there a way to fix it? Are there any plans from Microsoft to fix these bugs?
Thank you.