You sure you don't have something blocking things at work? Attached images would be residing on different servers, ones that might trigger something like websense or something like ad blocking technology.
Not sure how computer savvy you are, but you can test this. If you can find a picture that isn't pulling up and post a link to that thread, we can give you the link to where the picture is. Then, try hitting just the picture with your browser (maybe you can do 'view source' and find it; not sure what your computer skills are)
That would eliminate anything outside of your browser in most cases. At that point, it's probably a setting somewhere, a virus, spyware, etc. on your computer.
If you think it's AVG, try checking any real time monitors or virus programs running. Not sure if it has an internet watchguard running at all times or something similar. It could be that it's not allowing the browser to hop to addition machines for security reasons. Might be a part of the redirection settings. Haven't seen this myself...just taking educated guesses.