Preseed with wheezy overwritting interfaces file

[ML mail <mlnospam@yahoo.com>]

Hello,

I
 am installing wheezy automatically by using preseed and am using its 
late_command feature to run a script at the end of the installation. 
This script is actually modifying the /etc/network/interfaces file to 
setup bonding and VLAN access. This all used to work fine on squeeze but
 now with wheezy it looks like the /etc/network/interfaces file gets 
rewritten after the late_command of preseed.

Does anyone know more about this or have any tips?

Regards.
John