I have instances of using OnClientBlur on multiple RadComboBox controls, and if you tab quickly enough the event does not fire. I've created an example which replicates what I see in the project I'm working on - two RadComboBoxes with the Blur event where I get the second to fire but not the first when tabbing from first to second to third (just another control w/o event). This is causing issues where some validation is bypassed. Screencast: http://screencast.com/t/VTQrN9uOVrI9 A couple observations: - It will fire correctly if I wait long enough before tabbing out. - If I pause on the second control after tabbing, then click somewhere, it sometimes then fires the Blur from the first control. - I am using LoadOnDemand. From my general observation it looks like it's potentially a race condition with the loading.