Regarding Grid Resizing

Hello,
I am doing my project on activewidgets. I am having some doubt, which i need to clearify. Actually i have given one combo box in my grid. so that when i am selecting particular data from combo then the thing available in that all are coming. but when once again i put "all" in combo in combo so that i can get all the data available in grid, then i can't able to get. But when i will use scroll, I am able to get data. so i would like to know why the data is coming after scrolling only. why its not coming by itself.