> all the time the file i'm interested in containt this 
> message in the hts-log.txt :
> 'WARNNG: File has moved from 
> img2.hebus.com/moteurs/cars_bmw/cars_bmw_007.jpg to 
> <http://www.yahoo.com>

The site is filtering robots and offline browsers like 
httrack (maybe because some users abused bandwidth)
You can bypass this using the User-agent field in the 
Options, *BUT* first:
- use reasonnable bandwidth limits (such as 10 KB/s : see 
Set options / Limits / Maximum transfer rate)
- use NO MORE than 1 or 2 simultaneous connections (1 is 
prefferable) : set Options / Spider

I insist: USE REASONNABLE LIMITS! if not, you may be 
banned, and even reported for network abuse (remember than 
downloading at fast speed can slow down websites)