Try rebuilding your project to fix problems.
I've been following the steps of a series of articles on building JSF applications with WSAD. I first created the web project without support for Faces and WDO. Later I added these support from properties dialog of the project. And later when it comes to inserting a WDO Data List, problem emerged, I cannot insert the WDO List into the page, not after I pressed Finish of the wizard, nor when I dragged it from the page data view, even after restarting the workbench. I then tried rebuilding the project and inserting the WDO List again, it worked. I think this is caused by some kinda project information refreshing problem, that is, although I added WDO support after I created the project, the information on which insert WDO List mechanism relies still shows that this project has no WDO support, so I cannot insert anything WDO dependent.
I don't know whether this can be called a bug. So, the conclusion is, try rebuilding your project to fix wired problems like this one. If anyone has any idea about how this problem come to pass, please reply.