I emailed YPN support yesterday and asked if I could use Adgenta with YPN ads on the same pages. Adgenta ads look similar to Adsense/YPN, but are not contextual - you control the ads by setting keywords or a category.
Support replied they are NOT allowed on the same pages as YPN. I can only use them in "other" pages that do not carry YPN.
I have not asked Adsense yet, but I figure I can use Adgenta with Adsense since the ads are not contextual - I probably need to set a different background color too.