One way to correct this issue is the "brute force" approach. You simply delete the site and rebuild it. It gets the job done, but you have to set the whole site up again which may or may not be trivial.
The other way to fix this is to (gulp) edit the registry. Here is how you go about fixing it (Windows only, I'm afraid. I don't know the first thing about a Mac). These steps are for DW8, but they pretty much work with the last two versions as long as you can find the site keys.
- Close DW8
- Open the regedit application (start|run|type "regedit"|enter). That should open your registry file in the editor
- Back up the registry! I can't stress this strongly enough. If things go wrong, you want a copy of this thing that you can at least examine and at worst restore. You may also want to keep a bootable cd around just in case lightning strikes.
- In regedit, drill down to \HKEY_CURRENT_USER\Software\Macromedia\Common\8\Sites
- You now need to select the site number that is having problems. You will see numbered entries like -Site0, -Site1, etc. You can find your site by looking at the SiteName key under each site entry.
- Locate the values that start with "Local Expanded Dir " and ending with a number. There might be quite a number of them. Go ahead and delete all of them.
- Next, find a key called "Local Expanded Dirs". Double click the entry and change the value to "0" (zero).
- Close regedit.