I've tested this site the next day and it worked. Now as it turns out I run my testserver on IIS. The strange thing is that it kept keeping changing the file permissions so Dreamweaver couldn't copy the right files onto the testing server. I discovered this by accident. I've set up some new testing sites just to test if I could reproduce this error but all went well. Then with using digital file pro I ran into trouble again. IIS keeps changing the user permissions at random. I'm happy that my production server is a VPS running on Linux and Apache.
Thanks for looking into this..