you recently tidied up the code in trunk to use the ConfirmPassword field. As a side effect of that my layouts had been messed up because now the registration form has nested class="middleColumn" divs.
Well I'm picking this is what the ConfirmPasswordField throws out so I would need to change that core field holder. It wouldn't be a patch for the forum (unless we go back to the duplicate password fields which was the reason we hit the security issue)
How about a switch in ConfirmPasswordField to set "noWrappingDiv" (if this wrapping div is really needed and uses somewhere, however i wouldn't be surprised if it is not needed anywhere and can be taken off completely).
For now the only option I see is to try to workaround it by throwing some more CSS rules at it. Or you change ConfirmPasswordField ;)