I am having this same issue. I have a brand new MacBook Retina 16GB ram, 768GB SSD with 10.8.3 and Fusion 5.0.3. I started with 5.0.2 I believe and then updated to 5.0.3. With 5.0.2 I had to turn off the video acceleration features to get it to work at all but in 5.0.3 I could enable it and see the areo display in Win7 just fine. However, it immediately started hanging for 10 to 30 seconds several times an hour. I also found that it would often be slow to respond to typing.
I don't use it that much and it hasn't crashed my system yet so I will try and make do until the next update.