Version:            (using KDE 4.0.83)
Installed from:    Ubuntu Packages

With two keyboard layout enabled, I sometimes have trouble typing after switching between them. Recently, after switching from English to Hebrew with Firefox as the active application and Kate and Kmail open in background tabs, I found that I could not type in Firefox. I switched back to English and did some tests:
1) In Firefox I could not type text, the arrow keys (left and right) worked, backspace did not work, the delete key worked.
2) In Kate I could type text, however the arrow keys did not work, backspace did not work, the delete key did not work.
3) In Kmail (embedded in Kontact) I could type text, the arrow keys did not work, backspace works, the delete key did not work.

There was no problem using the mouse in any application. This condition is semi-reproducable, in the sense that there are keyboard problems after switching keyboard layouts. The specific problems vary from instance to instance.