This is how it works in Firefox:
In photobucket, go to your account options, you'll see this on the left in there:
Click on link options, and choose which links you want to have visible with your thumbnails and save. (I've circled the one for forums):
When you go back to your album, it should show the links you have told it to show with each thumbnail, like this:
Click inside the link box once, then right click and choose copy:
Come back to the forum page, and rightclick inside where you want to make a post, then click paste and the link should show up in the message box.
From there it's just a matter of finishing off the post as always and clicking on post

Anna