Error 450

At the end of each files I upload it says 450 Transfer aborted. Link to file server lost.
The files doesn't work good, ie rar can't be extracted.
:?
I'm using latest SmartFTP with passive mode and through http proxy.
What can be wrong ?

Any help is appreciated

Please could you post an example log.

200 Type set to I.
PASV
227 Entering Passive Mode (209,218,193,26,2**,2**).
Opening data connection IP: 209,218,193,26,2**,2** PORT: 56017.
STOR Crack_Zanzarak_Fr_V1[1].0.1.0.exe
150 Opening BINARY mode data connection for Crack_Zanzarak_Fr_V1[1].0.1.0.exe
26624 bytes sent successfully. (13.00 KB/s) (00:00:02).
450 Transfer aborted. Link to file server lost.
TYPE A
------------------

The file gets uploaded, but not 100% it seems.

Thanks.