Nicko.
I had the same problem & I know how F*****G frustrating it is!
I tried the "Tiny'URL" & that didn't work either, but I worked out what I was doing wrong.
What you need to do is the following.
I opened 3 web pages. 1 the forum, 2 the Photobucket site, 3, the Tiny.URL site.
Go to your Photobucket site & copy the image URL you want.
Paste that into the Forum thread you are posting.
This is where it gets important.
You will note that the tag has [IMG] at each end. You DO NOT shrink this in Tiny.URL machine, as that is what makes it not work.
You need to copy the rest of that link (NOT the [IMG] bits).
Then paste that URL into the Tiny.URL site. This will shrink.
Then, once you have the new shrunken URL, copy that & paste it over the TOP of the old url on the forum post, remembering to leave the "[IMG]" at the start & the finish.
THEN IT WORKS!! Woooo Hoooo.
Goodluck.
Let me know if you have anymore problems.
Rob J