see this page for details on troubleshooting FTP connections in Dreamweaver:
troubleshoot-ftp-issues-dreamweaver-cs5.html
If that does not solve the problem, you may need to try renaming the users configuration as outlined in step 12 of the Adobe troubleshooting guide:
troubleshoot-javascript-errors-dreamweaver-cs4.html#main_user_config
if you still have problems after trying those steps, i would recommend contacting Adobe's support


