With the way you assemble this (over a period of days), I'd probably do the "assembling" in something else (like Notepad/Word/Wordpad) from the start.
When you have it all put together on Sunday, THEN start a new thread here, copy/paste over your assembled quiz, preview it and fix any format differences that may exist, and submit.
Right off the top of my head, I'm not familiar with the exact problem, but it's obviously some sort of timeout function of VBulletin for a new thread creation.