There are two possibilities that I know of. It could be one or both.
1. This is something YOU can do. Turn off all Pop-Up Blockers EXCEPT Internet Explorer. (i.e., to turn off Yahoo Pop-Up Blocker, in the Y!Toolbar, click on the Pop-Up Blocker Button; click "Disable Pop-Up Blocker".) Turn off any others you may have EXCEPT IE.
See if you can view the pictures now. They may need to be re-sent.
2. This is what SENDERS need to do if they use Outlook. Then, they will have to re-send the pictures:
In Outlook, click the Tools menu,
click Options.
Click the Send tab,
click HTML Settings.
Make sure that "Send pictures with messages" is selected.
Then resend the pictures/images.
(There may be similar settings in other mail programs, if they are not using Outlook.)
Will you let me know if these solve the problem? I can keep thinking on it ....
Peace.