Please check your signatures. It looks like the conversion process added extraneous characters to links and links to growlists point to the old Ikonboard.
So you'll have to find your growlist posting and relink the vBulletin board reference.
When checking your signature, use the "enhanced editor" mode vs WYSIWYG. Click on the button (with the two letter "A"s in the upper right corner of the message editor window) to change mode if enhanced editor is not your default.
The extraneous characters are normally a \" or the hexadecimal notation of %5C%22 surrounding the url for your link.
It's driving me nuts seeing the \" or clicking on a link that doesn't work