Windows 7 SP1 x64
Spark 2.7.2.695 (Russian)
Java 8 Update 31 (both x32 and x64)
After some unspecified action users are no longer available to change their keyboard layout in Spark.
Layout letter does change to Russian, but text in the message window is typed in English.
Restarting Spark solves the problem just for a few minutes.