I always grate my cheese before freezing and that works fine. Also you can take out just as much as you want at a time as it doesn't all stick together.
balearic is right , my parents live in france and we always take a large block over when we go on holiday and they freeze it into smaller portions, it just tennds to make it slightly crumblier so they have told me.
It does make it slightly crumbly, but grating cheese in its frozen state makes it much easier,as long as you protect your fingers from the cold with a kitchen towel.