WORKAROUND:

Run both the full and differential/incremental backups to the same storage media type (both to tape or both to disk).

Symantec Corporation has acknowledged that the above-mentioned issue is present in the current version(s) of the product(s) mentioned at the end of this article. Symantec Corporation is committed to product quality and satisfied customers. 
 This issue is currently being considered by Symantec Corporation to be addressed in the next major revision of the product.  There are no plans to address this issue by way of a patch or hotfix in the current or previous versions of the software at the present time.  Please note that Symantec Corporation reserves the right to remove any fix from the targeted release if it does not pass quality assurance tests or introduces new risks to overall code stability.  Symantec's plans are subject to change and any action taken by you based on the above information or your reliance upon the above information is made at your own risk.
 
Please be sure to refer back to this document periodically as any changes to the status of the issue will be reflected here.
 
Please contact your Symantec Sales representative or the Symantec Sales group for upgrade information including upgrade eligibility to the release containing the resolution for this issue.  For information on how to contact Symantec Sales, please see   http://www.symantec.com