I have just experienced something similar to what BenJ experienced. For some reason I cannot select an object, lasso, pan, click and drag on my screen, also the lines will not stay highlighted and wont resize. My Classes are on Show/Snap/Modify Others and my Layers are Show/Snap Others. It was working fine earlier and somehow my workspace just stopped responding. I am able to zoom with the scroll bar.
How can I remedy this asap, I'm desperate!