Can you please clarify something for me? Is the problem related specifically to the images, or is it that the amount of text in the post is too long? (You should get a quite specific warning when that happens. I know, I've seen it
)
The reference to a Yahoo message is a new one on me though.
There is a setting on the forum that disallows images greater than 800px wide. It's normally set to avoid huge pictures stuffing up the layout of a thread.
I've disabled it for now, so can you see if the problem persists?
cheers
RET