When trying to drag a window the whole screen becomes laggy and some windows when dragged do not even appear until I release the mouse. They do appear where the window was suppose to end up after the drag but the dragging animation that happens while dragging is not seen.

I am using a NVIDIA 9500 GT 1GB with the proprietary drivers, an Intel Core 2 Duo 8500 and 4GB RAM just to make sure that this is not the problem. In 11.04 it worked correctly when dragging.