When I export my HTML file from FW CS6 and preview the site in the Browser it looks fine but when I open it up in DW to look at the site images are all over the place from the slices. I've been trying to find a workaround to fix this but to no solution.
Below is how the site looks in DW
I was having the same problem, and after much experimentation, I found that by changing the output to Dreamweaver XHTML instead of Dreamweaver HTML under the "Options" corrected it for me. Hope that helps you too!