I´m new here. Also with CM. Well... I did a test.. I sent an email to Outlook 2007, Gmail & Hotmail.
I read them showing images and did some clicks... But the reports still appears with 0% Opened and 0% Clicked.
We've never seen an example of this happening - if you click a link (with tracking) and end up at the correct URL, then we have definitely recorded the click.
Can you please contact support with some specific details about which campaign and client, and we can take a look for you.