For some reason, I have the same problem. :/
So Imageshack's pictures work when you are trying to save an image?
I suggest you to make a picture album, if you want to save images here in the forums:
1. Go to your User CP
2. Press "Pictures and Albums" from the category "Network" (the vertical banner on the left)
3. Now press "Add Album"
4. Make a title (description is optional) and choose the type of the album (Public, Private or Profile)
5. Now you have an album. Press "Upload Pictures"
6. Upload the pictures from your folders, and submit.
Now you have images saved to your profile. When you go to your album, and press the picture you have uploaded, it shows you the full sized picture with the picture's URL and BBCode.
Hope this helped.