Design view in Dreamweaver has never been 100% accurate - it's really a gross aproximation of what your page looks like (if that). And it typically fails when there's floats or more complex CSS positioning occuring. I'd just ignore it it and work in code view (or split code/design view) and test in a browser.
And, CS3 was often confounded by floated layouts. CS5 is MUCH better.
Oops - sorry for the redundant comment!
Message was edited by: Murray *ACP*