Wondering if the problem is at DreamHost's end (possible, but less likely), or at your end...
Is the link in the panel something like
Can you connect using command-line ftp in a dos/cmd box?
Enter your user and password when prompted.
Enter "quit" to exit FTP.
Back to your original question, you could see if you have something (PC firewall or ISP) blocking FTP/port 21?