An Opportunity history can contain several types of items.

Some of those items are BCM items (e.g. phone logs), some are Outlook
items (e.g. Tasks and emails), and others are files (e.g. Word
documents). BCM items are automatically sharable because they are
stored in the BCM database, Outlook items are only shared if both
users are using the same Outlook store (e.g. Exchange), and file items
are only shared if both users can access the file on the same shared
folder. If an item in the history cannot be opened, BCM will display
the information it has on that item, but it cannot open the actual
item.

Luther
http://beyng.blogspot.com/

Shawn, I have the same issue, did you ever get an answer?