Walls won't join in elevation

[buzzer1001]

I don't know why, but walls aren't cleaning up in elevation in any of my Revit files. Exactly the same wall type, exactly aligned in plan, do not overlap in height (bottom / top of walls are set to the appropriate stories with no offset). I created a brand new file with just two walls to demonstrate.

I've done a test print, as I've read that Revit can just do this on screen to save processor power...but no cigar.

Is there a global setting to change?http://forums.augi.com/attachment.php?attachmentid=99681&stc=1