Thanks for taking the time to report this bug.

The crash might be related to the fact that you could have a connection entry in ~/gnome-commander/gnome-commander.xml with a cleartext password. See bug #653573. 

So, please:

1. Close GCMD
2. Open ~/gnome-commander/gnome-commander.xml, 
3. Search for the line related to your FTP connection in the "Connections"-section in the xml-file,
4. Delete this line in question, save the file and start GCMD again.

Now you have to set up the connection again in GCMD, so remember to keep the data you deleted in step 4 somewhere. 

If that doesn't help and GCMD still crashes while connecting to the FTP server, we need a stack trace to find out what caused the crash. Can you get us a stack trace? Please see http://live.gnome.org/GettingTraces for more information on how to do so. Thanks in advance!

Thank you for your answer. Now I have a 'simple' crash instead of freeze :)
What I did:
1) Delete the <Connections> section from ~/gnome-commander/gnome-commander.xml file.
2) Delete the old  ~/gnome-commander/connections file (it was still there)
3) Start the gnome-commander, open Remote Connections (Ctrl+F, but I'm not sure, what are the original English names, I use it in Hungarian)
4) Click Add, choose FTP (with login), fill in Alias and Server, and click OK
5) Click on Connect
6) ...and now the Gnome Commander closes immediately, without saving the settings.

The gdb output was the following:

Starting program: /usr/bin/gnome-commander 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

(process:4218): GLib-GObject-WARNING **: Attempt to add property GnomeProgram::sm-connect after class was initialised

(process:4218): GLib-GObject-WARNING **: Attempt to add property GnomeProgram::show-crash-dialog after class was initialised

(process:4218): GLib-GObject-WARNING **: Attempt to add property GnomeProgram::display after class was initialised

(process:4218): GLib-GObject-WARNING **: Attempt to add property GnomeProgram::default-icon after class was initialised
[New Thread 0x7fffe7ec9700 (LWP 4220)]
[New Thread 0x7fffe76c8700 (LWP 4221)]
[New Thread 0x7fffd7527700 (LWP 4222)]
[New Thread 0x7fffd6d26700 (LWP 4223)]
[New Thread 0x7fffd6525700 (LWP 4224)]
[New Thread 0x7fffd5d24700 (LWP 4226)]
[Thread 0x7fffd5d24700 (LWP 4226) exited]
[Thread 0x7fffd6d26700 (LWP 4223) exited]
[New Thread 0x7fffd6d26700 (LWP 4227)]
The program 'gnome-commander' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadLength (poly request too large or internal Xlib length erro'.
  (Details: serial 15694 error_code 16 request_code 94 minor_code 0)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the --sync command line
   option to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)
[Thread 0x7fffd6525700 (LWP 4224) exited]
[Thread 0x7fffd7527700 (LWP 4222) exited]
[Thread 0x7fffe76c8700 (LWP 4221) exited]
[Thread 0x7fffe7ec9700 (LWP 4220) exited]
[Thread 0x7ffff7faea00 (LWP 4218) exited]
[Inferior 1 (process 4218) exited with code 01]

Some additional info: After I store the FTP password in the Gnome Keyring Manager (e.g. using Tux Commander) then I can connect via GCMD without any error or crash.

Hi again,

thank you for your response. So, there seems to be a strange problem related to the cooperation of GCMD with the Gnome Keyring manager. I heard this from several people now, so this issue has to be investigated in the future. Unfortunately, the error message in your comment is not very meaningful to me, though. But I will have an eye on that problem. Fortunately you found a workaround by now with the help of Tux Commander. Great!

Some people reported also that it helped to reset their Gnome Keyring when they had connection problems with GCMD while using the keyring manager. But I think that this is not the best solution... :-/