When you say “Freezes” do you mean you computer completely freezes or just audio drops/performance spike? Mine does it 3 or 4 times a song as well but when it does it my mouse still works etc … just Cubase freezes with the audio dropping. If I’m using midi it sometimes causes a midi lock and I have to hit the “reset”.
In Cubase 6.5 I kept my buffers below 512 and only set it to 512 when I was working on a large project. With 7 I keep it on 1024 and I still get the spikes.