Several customers have been migrating from CRM 2011 Online to CRM 2011 Onpremise in recent weeks. When building a test environment, I realized that the customizations from the CRM 2011 Online would not import into CRM 2011 On Premise.
After further investigation, the CRM 2011 Online customizations file contains an entity called visualization. This entity was used for the older CRM 4 Online dashboards and is not present in the On-premise versions.
Edit the XML to delete this entity, rezip and import! Enjoy.