When using a RadButton with icons, when the mouse is over the icon, it should display the PrimaryHoveredIconURL. Then when you move the mouse off of the icon it should change to the PrimaryIconURL.
This works fine in most cases. However if you have a client event on the button - OnClientClicked - that launches a RadAlert, when you move the mouse off the button to close the RadAlert, the icon does not change back to the PrimaryIconURL. So you are left with an icon that appears to be hovered. It 'fixes itself' once you move the mouse back over the icon and off it again.