Uploading problem

Uploading wasn't a problem last week. Without making any changes, today it no longer works.

Here's a log:
[11:47:32] SYST
[11:47:32] 215 UNIX Type: L8
[11:47:32] Detected Server Type: UNIX
[11:47:32] FEAT
[11:47:32] 211-Features:
[11:47:32] MDTM
[11:47:32] REST STREAM
[11:47:32] SIZE
[11:47:32] 211 End
[11:47:32] PWD
[11:47:32] 257 "/" is current directory.
[11:47:33] CWD /images
[11:47:33] 250 CWD command successful
[11:47:33] PWD
[11:47:33] 257 "/images" is current directory.
[11:47:33] TYPE A
[11:47:33] 200 Type set to A
[11:47:33] PASV
[11:47:33] 227 Entering Passive Mode (195,130,132,84,7,106)
[11:47:33] Opening data connection to 195.130.132.84 Port: 1898
[11:47:33] LIST -aL
[11:47:33] 150 Opening ASCII mode data connection for file list
[11:47:33] 3046 bytes transferred. (63,2 kB/s) (47 ms)
[11:47:33] 226 Transfer complete.
[11:47:40] Remote file exist check: "axe.bmp".
[11:47:40] TYPE I
[11:47:40] 200 Type set to I
[11:47:40] SIZE axe.bmp
[11:47:40] 550 axe.bmp: No such file or directory
[11:47:40] File size check (SIZE) failed. File not found or permission denied.
[11:47:40] PASV
[11:47:40] 227 Entering Passive Mode (195,130,132,84,7,108)
[11:47:40] Opening data connection to 195.130.132.84 Port: 1900
[11:47:40] STOR axe.bmp
[11:47:40] 150 Opening BINARY mode data connection for axe.bmp
[11:48:40] 40960 bytes transferred. (682 bytes/s) (00:01:00)
[11:48:40] 550 Failed to contact Content Security Server
[11:48:40] MDTM 20070716073753 axe.bmp
[11:48:40] 550 20070716073753 axe.bmp: No such file or directory
[11:48:40] TYPE A
[11:48:40] 200 Type set to A
[11:48:40] PASV
[11:48:40] 227 Entering Passive Mode (195,130,132,84,7,113)
[11:48:40] Opening data connection to 195.130.132.84 Port: 1905
[11:48:40] LIST -aL
[11:48:40] 150 Opening ASCII mode data connection for file list
[11:48:40] 3110 bytes transferred. (64,6 kB/s) (47 ms)
[11:48:40] 226 Transfer complete.
[11:48:40] Transfer failed. Use the Transfer Queue for automatic retries.

The Opening BINARY mode data connection stops a little over 40%, no matter which file I try. But not always. Usually all I get is a "transfer completed" immediatelly followed by the contradictory "transfer failed" message.

The file name is uploaded, so something must be getting through, but size stays 0.