Well, what Google says is you cannot use AdSense together with a similar type of adds.
It's not a lot more precise than that, but I have seen many web site using services as click in text
which is highlighting words in content with commercial links. And even more with pop up adds used together with AdSense.
What would really be impossible I guess would be to use AdSense with MSN Adds.
Anyway, if you want to be sure, you can trey writing Google a nice and gentle mail to ask for confirmation.