Combobox flicker on value selection and tabbing


I am using Vaadin 7.1.7.

I have 1 simple ComboBox with around 4-5 values and another ComboBox with 4-5 values again within a FormLayout.
Now, on focus on the first ComboBox, I use the keyboard to select any of the values and then press ‘Tab’ to go to the next CombBox.

What I notice is a small flicker on the first ComboBox before my value is set into it. I was wondring if there is some explanation for this behaviour?

We are using IE 8. But i notice the same behaviour in latest versions of FireFox and Google Chrome browsers.

Thank you in Advance!