sounds like some obscure bug.
if you are still experiencing this and you have Vista SP1 installed then you should file a bug with PSS.
Thanks to all. Found the problem. It was program(Punto Switcher) that changes keyboard language layout as you type. As soon as I disable this program it's start working without any problems.
- Proposed as answer by Marc1968 Tuesday, July 15, 2008 8:09 PM