You receive the error "Cannot import this web part" when you try to import an exported TagCloud Web Part in SharePoint 2010

Symptoms

When you try to import an exported TagCloud Web Part into a Microsoft SharePoint Server 2010 page, the web part does not appear on the page, and you receive the error:

If you try to upload the exported TagCloud Web Part into the Web Part Gallery, you receive a Runtime Error exception. The Event Viewer displays a WebPartPageUserException exception.

Workaround

To work around this issue, you can save the TagCloud Web Part as a *.dwp file from the Web Part Gallery.