This is also a long standing problem with scim. As long as I started scim as my input method (either English or Chinese), fontforge (all versions) will stop accepting key-strokes for any dialog that needs input (for example, menu View\Goto). This is repeatable on CentOS 4.x~5.x and Ubuntu 6.10 ~ 9.04. Only when I started fontforge remotely, and display with a local Xserver, I can type with scim.
My desktop language is English. I used scim normally for typing Chinese. Typically I only enable "English/Keyboard" and "Chinese(simplified) Ziranma" as my input engines.