compression washer tap valve too big?

This is an odd one! I have a bathroom sink where the hot tap has a compression valve. I can easily loosen the valve but I cannot then remove it from the tap! It seems that the far end of the compression valve is wider/as wide as the thread of the valve. Is this a recognised issue? Is there any way of removing this valve, or do I need to replace the whole tap? I can provide an image if required!