I use CS5 and haven't had any problems. You really need to follow the signcut install instructions exactly and install the plugin. We had to do this a few times to get it right.
We are advised to save the AI files as EPS v8 or so, but I never do and it opens up fine. Make sure you convert text and lines to outlines and do pathfinder>merge. If you don't, you can end up with wonky cuts, it cutting the design twice,etc.