I have shifted by Dev Env recently to Eclipse Helios on Windows 7. After that the Ctrl + Space Content Assist feature is not working. I found out that that key option is utilize
@Polac - Thx. That's what fixed it for me. I'd hit ctrl+space and I'd get a popup for chinese character selection. I have Windows 7 so for me it was: Control Panel -> Region and Language -> Keyboards and Languages tab -> Change keyboards... button -> Advanced Key Settings tab
Be warned, its stubborn. I tried to just clear them, but as soon as I applied the settings they reset back to using the original key bindings. If I change the key binding to something obscure they still reset sometimes. It's annoying. Maybe its just my OS installation that's goofed, but it could be a Microsoft bug.
Didn't need Chinese on my system, so I removed it as an installed language in the first tab and that finally got rid of the hardcoded Chinese key bindings.