As we keep saying avast doesn't have any function to block images or anything else for that matter. If it did, why doesn't it block ALL images on all pages ?
Do you have any other ad blocking software which might block the location these images come from ?
Can you give some examples of URLs where images don't display and we can try them ?
If there is some form of interaction with a program/process and avast then removing avast may well resolve that conflict/interaction, but what it doesn't do is identify exactly what is at fault.
With Web Shield enabled, did you clear your temporary internet files or do a forced page load as we suggested ?
Did it work (in displaying the images) or not, you didn't say ?
Have you tried a different browser ? - firefox, opera or any non IE based browser.
If it were a definite problem with avast! web shield, IE and Kerio in combination (a popular set-up) then there would be numerous threads relating to the problem, I just don't see that.