[6/09/2011: Update : this bug has been fixed in the June CU]
Found a new Sharepoint 2010 bug : we cannot mix-up Reusable content and Web Parts in a publishing field.
This bug has been submitted to Microsoft.
We can reproduce this bug in the Information Worker VPC. Here are the steps:
1. Create a new web site based on the Publishing Portal template or on the Enterprise wiki.
2. Go to View All Site Contents, click on Reusable Content
3. Add a new Reusable Text content and save it :
4. Go back to View All Site Content
5. Select Pages and add a new Page based on the Article Page content Type-Select the Body only Page Layout.
6. Click on the generated page and move it to Edit mode
7. Move the cursor to the Page Content field; In the Editor menu, select Insert Reusable content and add the content you did previously
8. Add an existing web part or an existing list (like Documents) after the reusable content.
9. Click on Save & Close and here is what you get : the reusable content is lost