problem with IMG inside URL tag

[SDB]

On my forum, if I add an IMG tag inside a URL tag, in order to make the image clickable, when submitted, the URL address is substituted for the url of the image itself, not the URL specified in the URL tag.

Anyone seen this before / have any ideas?

I have vbSEO installed, and am wondering if that is causing a problem, but when editing the post, the code has actually been changed, so suspect not.

Thanks