The data-view web part is one of the more powerful tools in the SharePoint arsenal, allowing you to completely customize (and control) the data displayed by a basic list-view. I was rather taken aback when I discovered that in SharePoint 2007, I seemed to lose my customizations when I imported my customized web part to a page.
The good news is the SharePoint Team is very aware of the issue and it is being considered for a future fix. They were also kind enough to let me in on a little secret for getting around this issue.
The problem lies in the fact that the view is using the full tool bar. If you have the “FULL Toolbar” enabled when you export your data-view web part, you will lose your customizations when importing it. The trick then obviously is to ensure you have only the minimal, or no toolbar enabled before exporting your web part.
Hope it helps