This might be a very unusual case: we have one single teamsite which acts like a model for +20.000 other teamsites.
Changes made to this teamsite are copied to the others by using the Import-Export functionality of the WSS API. Because we do not want the actual content to be copied we only copy certain files; to simplify, lets say we only copy the default.aspx page.
The list and library structure is maintained through content types, every site has the same list and library structure. In the future new lists can be deployed with Content Deployment (import-export) or by script.
After we run the import (so the default.aspx pages in all sites are updated) everything looks all right; except for the list-view webparts. Although they are nicely attached to the local lists of their new environment, the 'changes' made the the views and toolbars are lost.
On one hand I can imagine this is a unsupported scenario; you cannot guarantee the list even exists in the target site.
On the other hand this issue is very similar to the "Changes that you make to the 'List View' Web Part are not retained after you save the site as a template in Windows SharePoint Services 3.0" issue: http://support.microsoft.com/kb/926284
I can't tell yet if this is really a bug. But I can tell you our workaround: use Content Query Webparts. This also has a big advantage of centrally managing the layout, which in this situation is a big plus.
koning53