While getting started with Sublime I found that the key sequence for auto complete (ctrl+space) wasn't working for me. Instead, the key sequence was hijacked by Windows, and switched my keyboard language to Chinese. Very annoying.
The fix is:
1. Open Windows Control Panel
2. Open the Regional and Language Options settings
3. In the Keyboard and Language Settings tab, open the Change Keyboards dialog
4. Remove all the languages you don't want
Obviously this will remove support for a Chinese language keyboard, but assuming like me you are not a Chinese speaker, this won't be a problem.
Now, the Ctrl+Space shortcut is free for Sublime to use.
Apologies if this has been covered previously, I searched the forum but couldn't find a mention of the problem.