I've just commited a fix for a bug that prevented us from connecting to FTP sites using bookmarks or credentials.
It will be available in tommorow's nightly build - please check to see if it resolved the problems you had.
Regarding the second section of your original post ("Also, after disconnecting from FTP server, nothing happens. I can still browse FTP, than my local drive, than again same FTP, than disconnect from already "disconnected" server, and so on, endlessly.") -
It's not a bug. The things that should happen when you select to disconnect from FTP server is that the connection to the FTP server is closed, and the previous folder is still presented on your screen. if you try to enter another location on the FTP server or switching to local file and then back to location on the FTP server - that's ok, the connection will be re-established.
In other words, when the user disconnect from FTP sites it's ok that nothing that he could see happens. the connection is closed without affecting the presented screen.
Thanks for reporting,