I believe your dreamweaver's FTP settings have been reset, and when you attempt to upload your files back onto the site to update them or simply modify them, your dreamweaver client does not connect to the server properly.
This isn't much help, but it will hopefully lead you to a solution.
I'm using Dreamweaver and have built my own website. Everything was fine until I recently re-installed XP, and now I can't make any changes. I'm not a web expert, and I can't remember how things were set up first time around, but I was able to edit it before. I've definately got the correct login details because I can download the site onto my computer, but if I make a change, nothing happens on the site - even after several days of waiting (updates used to occur after a few minutes). I am hitting the 'put' button.
Any ideas what I might be doing wrong?