Solution for: WARNING **: Error converting text from IM to UTF-8: Conversion from character set '646' to 'UTF-8' is not supported

I had some problems with applications ran under X server on Solaris systems. When I tried to type any characters into some textbox in that applications the characters wasn't entered and the console has the following output:

One message after application start:
GLib: Cannot convert message: Conversion from character set 'UTF-8' to '646' is
not supported

And many messages like this:
** (gedit:14860): WARNING **: Error converting text from IM to UTF-8: Conversion
from character set '646' to 'UTF-8' is not supported

I haven't found any solution on the internet, but that was pretty simple to fix. It's enough to right-click in any textbox of application with that problems, and select "Default" menu item from the "Input methods" submenu of opened context menu. Hope someone will find this helpful.