I believe a man can love more than one woman, just as gmcmeee said... There are different types of love.. even different types of romantic love.
I think we can certainly be in love with more than one person at the same time but it will be a different experience with each individual.
In my opinion it is our posessive jelous nature that leads us to say men can not love more than one woman. We wish it were true. We all want to feel like the only woman in the world to the one we love, but that doesn't make it true.
I wish I could escape this posessive jelous nature in me, but it's just a part of who I am.