Convert ListViewWebPart to XsltListViewWebPart after migration

Hi,

I'm facing an issue after the migration of our sharepoint 2007 sites to sharepoint 2010. Some of my previous list (most of them are tasks lists, but not only) are still using the old ListViewWebPart instead of the XsltListViewWebPart. We cannot afford that as the 'add new item' button is missing, the tabular view is not working, and so on.

After some search, I've found threads where it's said that just editing the page/edit the web part and save will convert the web part to the new xsltlistviewwebpart... But it's not working, still the same. Event if i create a new view, the web part used by the new view is still the old listviewwebpart ...

Any ideas?

Thanks!