Resume upload a very big file

[imcsee]

* FlashFXP v[3 ].[0 ], build [1015],[*]registered
* OS[*] Other windows server 2003 ent
* Running behind NAT/router[*]
* Running firewall[*] No
* Running Antivirus[*] Yes, Name [mcafee]
* Network[*] xDSL
hello, my client is flashfxp 3.0 1015,
ftp server is xlightftpd 1.60a
file system of both side are NTFS.
when i upload a file about 4.xG
when i reboot my client pc,i can resume upload, but when I have
upload above 2G, it happens . i clck resume button, flashfxp said the offset is bigger than size of file , offset is reseted to zero. file transfer faied, and start to transfer next file.(i use a flashfxp version transferd to other language,so i can't paste the fxp debug info here.)
is it the bug of flashfxp , or xlightftpd ?