If the lineage of a file is unknown, the Origin functionality for that file will be disabled. So your situation is probably due to this limitation, rather than a problem with the Norton program. Usually, the Origin information will denote a URL from which a file was downloaded, so it may be that an attachment to an email message may not register as coming from a specific source.
Before NIS 2011 (18.5.0.125), NIS would always show me the actual email address that the virus came in on. This was available by selecting "Details" and then "Origin." Now, "Origin" is always grayed-out, even when I go back and look at the Quarantine history.
Does anyone see any "Origin" data when looking at the Quarantine history in NIS 2011? Is it with Outlook or another POP3 client?
Since the Quarantine History "Origin" is now unavailable for all previous viruses (some back to 2007), not just unavailable since installing NIS 2011 (18.5.0.125), it appears that the 2011 version has misplaced a pointer to the history data.