I just completed work on a Publishing Site collection for MOSS 2007 that is using a custom master page that I developed. The stylesheet that I am using holds all the overrides of the core.css. This includes web part titles etc. All the page layouts that I use are reflective of all the styles and use the Master Page as intended. When I go to edit the page and want to move web parts to different zones I no longer have that ability. The browser kicks back and error indicating an object required message everytime I select the web part i am wishing to move.
I am thinking that one of my styles might be causing this issue.