We upgraded to Confluence 4.3 from 4.1.4, and we notice that some images are not visible to Internet Explorer users. These include a few user profile icons, which is a minor point. Much more serious, none of the images from Balsamiq plugins appear. What appears is the red X, which is Internet Explorer's symbol for a missing image file. IE users can edit the Balsamiq plugins fine, but the results do not appear when viewing the page.
We have upgraded to the latest Balsamiq plugin version (2.2.1) which hasn't resolved the issue.