I am using a WebDropDown control (version 2010.1) and handle the client side events "focus" and "blur".

Most often anything works fine. But sometimes none of these events are fired. In those cases I can see, that the dropdown does not automatically opens when typing characters into the control. I can type characters, they are displayed and as soon as I leave the control, no blur event is fired. Next time I click the control and start typing characters the dropdown is opened as it should and as soon as I leave the control the events are fired correctly again.

What could be the reason for this?