Are you using Firefox or Internet Explorer? If IE, what version?
For firefox, at the top, click on Tools -> Options -> Content, and make sure that the box beside "Load images automatically is checked. If it is checked, click on Exceptions and see if anything is being blocked, ie Photobucket.com or TinyPic.com etc.
For Internet Explorer, try this;
for Internet Explorer (I have IE7, others should be similar) click on Tools -> Internet Options and click on the Advanced Tab.
Scroll down to Multimedia, and make sure the boxes beside Enable Automatic Image Resizing, Show Pictures and Smart Image Dithering are checked.
If you change anything, you need to restart IE for the changes to take effect.
If that didn't work, read on;
This is the advice from Microsoft.
Read more here; Microsoft Support