Not too sure how the built-in image posting works, I generally use something else -- you can use whatever image service you use, if the forum method gives any trouble.
I would normally do some checking myself, but I'm a long way away from my computer at the moment. If it wasn't so unlikely, I'd think it was a duplicate GUID. Maybe there's a more likely explanation, but it will be next week before I'm back at my desk.
If you can get the screenshot to me, then at least I could see what it conflicts with.