It won't cause a suspension, but it can cause other problems. Personally, I wouldn't do it as it would make your page look cluttered and unfocused.

You could try using a little script to alternate between adsense and publisher adverts per page view.

I thought YPN did not allow other contextual advertising on the same page or has this changed

Fromt the AdSense Help Files: [google.com]

You're welcome to display Google ads on the same site or page as other third party advertisements provided that the formatting or colors of the third party ads is different enough from that of the Google ads....