Finally, here are two different accounts in FlashFXP I have used for some time, these two accounts are for the same domain on the same server, and login successfully:
Live site: root access for modekungen.se
FlashFXP 4.3.0 (build 1933)
Support Forums
http://forum.flashfxp.com
Winsock 2.2 -- OpenSSL 1.0.1d 5 Feb 2013
[R] Connecting to Modekungen - live -> IP=109.74.10.201 PORT=21
[R] Connected to Modekungen - live
[R] 220 ProFTPD 1.3.3a Server (Debian) [::ffff:109.74.10.201]
[R] USER modekungen
[R] 331 Password required for modekungen
[R] PASS (hidden)
[R] 230 User modekungen logged in
[R] SYST
[R] 215 UNIX Type: L8
[R] FEAT
[R] 211-Features:
[R] MDTM
[R] MFMT
[R] TVFS
[R] UTF8
[R] MFF modify;UNIX.group;UNIX.mode;
[R] MLST modify*;perm*;size*;type*;unique*;UNIX.group*;UNIX .mode*;UNIX.owner*;
[R] SITE MKDIR
[R] SITE RMDIR
[R] SITE UTIME
[R] LANG zh-CN;zh-TW;fr-FR;ja-JP.UTF-8;ja-JP;ko-KR.UTF-8;ko-KR;bg-BG;en-US
[R] SITE SYMLINK
[R] REST STREAM
[R] SIZE
[R] 211 End
[R] OPTS UTF8 ON
[R] 200 UTF8 set to on
[R] PWD
[R] 257 "/" is the current directory
[R] PASV
[R] 227 Entering Passive Mode (109,74,10,201,206,78).
[R] Opening data connection IP: 109.74.10.201 PORT: 52814
[R] MLSD
[R] 150 Opening ASCII mode data connection for MLSD
[R] 226 Transfer complete
[R] List Complete: 1 KB in 1 second (1.0 KB/s)
Development site at modekungen.se/kopi
FlashFXP 4.3.0 (build 1933)
Support Forums
http://forum.flashfxp.com
Winsock 2.2 -- OpenSSL 1.0.1d 5 Feb 2013
[R] Connecting to Modekungen - kopi -> IP=109.74.10.201 PORT=21
[R] Connected to Modekungen - kopi
[R] 220 ProFTPD 1.3.3a Server (Debian) [::ffff:109.74.10.201]
[R] USER kopi
[R] 331 Password required for kopi
[R] PASS (hidden)
[R] 230 User kopi logged in
[R] SYST
[R] 215 UNIX Type: L8
[R] FEAT
[R] 211-Features:
[R] MDTM
[R] MFMT
[R] TVFS
[R] UTF8
[R] MFF modify;UNIX.group;UNIX.mode;
[R] MLST modify*;perm*;size*;type*;unique*;UNIX.group*;UNIX .mode*;UNIX.owner*;
[R] SITE MKDIR
[R] SITE RMDIR
[R] SITE UTIME
[R] LANG zh-CN;zh-TW;fr-FR;ja-JP.UTF-8;ja-JP;ko-KR.UTF-8;ko-KR;bg-BG;en-US
[R] SITE SYMLINK
[R] REST STREAM
[R] SIZE
[R] 211 End
[R] OPTS UTF8 ON
[R] 200 UTF8 set to on
[R] PWD
[R] 257 "/" is the current directory
[R] PASV
[R] 227 Entering Passive Mode (109,74,10,201,208,237).
[R] Opening data connection IP: 109.74.10.201 PORT: 53485
[R] MLSD
[R] 150 Opening ASCII mode data connection for MLSD
[R] 226 Transfer complete
[R] List Complete: 8 KB in 1 second (6.3 KB/s)
And again, second development site att modekungen.se/kopi2
FlashFXP 4.3.0 (build 1933)
Support Forums
http://forum.flashfxp.com
Winsock 2.2 -- OpenSSL 1.0.1d 5 Feb 2013
[R] Connecting to Modekungen - kopi2 -> DNS=modekungen.se IP=109.74.10.201 PORT=21
[R] Connected to Modekungen - kopi2
[R] 220 ProFTPD 1.3.3a Server (Debian) [::ffff:109.74.10.201]
[R] USER kopi2
[R] 331 Password required for kopi2
[R] PASS (hidden)
[R] 530 Login incorrect.
[R] Connection failed
[R] Delaying for 120 seconds before reconnect attempt #1