Do you have any language pack in V4? If yes, please apply the language pack in CRM 2011 and do the upgrade again.
If it still doesn't work, please log a support ticket to Microsoft. This issue need deeper investigation.
Thanks,
Jackie Chen, Microsoft Online Community Support. Please remember to click “Mark as Answer” on the post that helps you. This posting is provided "AS IS" with no warranties, and confers no rights.