Comment 2 for bug 90043

I tried shift_space, which is another shortcut, and the problem remains.

Okay I think I found how this problem comes around. This problem is highly CJK-related. In short, if environmental variable GTK_IM_MODULE is set to xim, the problem occurs, if it is set to scim, the problem disappears. Here is the simplified steps to verify the problem:

1. Open nautilus, press Ctrl+L to bring out the location bar, and right click in the location bar, find the "Input Methods" submenu, select "XIM". Now press Ctrl_Space or any shortcut to invoke scim, and you should be able to do so, because this problem doesn't exist in the location bar, but this way you set nautilus to use XIM.
2. Right click on a file/directory, choose "Rename", then press ctrl+space to invoke scim, now you should see the problem.

So, by default the problem doesn't exist; but it would still be a problem to many CJK users, since many of them would do "im-switch -s scim_xim", because this way env variables GTK_IM_MODULE and QT_IM_MODULE are set to xim, and is more compatible, for example, you don't have to mannually install scim-qtimm to input Chinese in QT programs, and Skype won't crash.

I'd really suggest the scim maintainer to adjust the symlink /etc/alternatives/xinput-zh_CN to point to /etc/X11/xinit/xinput.d/scim_xim instead of /etc/X11/xinit/xinput.d/scim as default. It would solve a few problems for novice Ubuntu CJK users. The only downside is this bug that I'm talking about here, hopefully you can find out why and fix it, then it would be perfect.

Many thanks.