I am not familiar with Norton anti-spam so cannot comment if this is your problem. You do not say which e-mail programme you are using.
However, a common cause of not being able to see/read attachments is due to the settings in Outlook or Outlook Express. There have been many threads on this subject on the forum.
With Outlook 2002, and 2003 attachments are blocked by default. This can be overcome by modifying the registry, (the Microsoft way). This is something many are wary of doing. However, help is at hand with a small programme which can be downloaded here:
I have used it for some months, and it works fine. The usual caveat should be observed; never open attachments that are from unexpected or unknown sources.