When using the Login Window (at start) if you select one of the bookmarks and try with the right button "Open in PuTTY" it doesn't work!
In fact, it works if all data is stored... even the password. If the password is missing then the connection fails.
To correct the bug one solution can be: Check first all parameters (username, password, address, port, directory, etc.) if someone is missing then try to connect with some default value; and for sensible data (like the password), leave the option to enter it.
I hope you can fix it soon.