Kickstart PXE redhat 5 over HTTP "error downloading kickstart file"

[M.B]

Need Help 
 
I tryed to install Redhat 5 Server and I get an arror popup meesage "error downloading kickstart file" 
"Unable to download the kickstart file. Please modify the kickstart parameter ......"
 
The ks.cfg file is on a directory under the document root of my Apache Server and its available when i tryed with wget command.
 
The vmlinuz  and initrd.img   arre correctly loaded  and anaconda is strating well. Few minutes later i get the message  "error downloading kickstart file"
 
DHCP, Apache are correctly configured and portfast is enabled in my switch Cisco.
 
I read sometimes in the Web,that  it seems a bug in anaconda and sontimes we sayed it works fine..
 
Some One have an issue for this ?
 
Bellow my PXE bootloader file
 
default KS
label KS
  kernel vmlinuz-5u3
  append ks=http://10.153.80.90/RH5U3/vms02 initrd=initrd-5u3.img ramdisk_size=9216 ksdevice=link ip=10.153.80.11 netmask=255.255.255.0 gateway=10.153.80.1 dns=127.0.0.1 keymap=fr lang=en_US.UTF-8 noipv6 nicdelay=40 linksleep=30 eth0_ethtool="speed=1000 duplex=full"

 
 


      
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