while playing back a web application some times it happens that the browser crashes and shut downs but the script in the test manager continues playing back even though it displays UAV error at the end in the log displaying the Desktop as a image (i think it captures the desktop when the browser shut down)

Could any one knows what would be the reason, As far as i think it could be the delay time which i have set (presently it is 1000 on my Robot setting)that could be playing back very fast.But I am not sure