Give the gift of Drupal. All merchandise is 50% off through 2016.
May be related to, but this is a fairly old issue.
My entire site runs under SSL, I'm using Mollom for captchas on webform nodes but browsers (in particular Internet Explorer) give warnings about insecure content on the page, IE being the worst with a popup warning which is less than ideal for our users. It seems like the problem comes from the image that is used in the Mollom captcha uses an http:// url, attempting to change this to https gives a 403 though.
Using the latest Mollom 7.x-2.x-dev branch.