I wanted to open a shared folder on my Windows 7 system under Ubuntu 10.04.
I clicked Places -> Connect to Server, selected "Windows share" as the service type, entered the server name and my login name, hit Enter, got a prompt for my password, typed it and hit Enter.
After entering my password, the password prompt opened again. This happened over and over.
Windows Live Sign-in Assistant is installed on the target system.
Uninstall Windows Live Sign-in Assistant and reboot the system.
Yeah, this one didn't make much sense to me. I had to do a lot of searching on this one.
Original Ubuntu thread I found the troubleshooting link in: