1 June 2013 build is out.

[NaN]

it says it can't load textures from

C:\Users\Benoit\Documents\VDrift/tracks/lemans_WIP/objects, data/tracks/lemans_WIP/objects

But my Vdrift is installed on D:\Vdrift\..... !

It looks in multiple paths for the data:
1. C:\Users\Benoit\Documents\VDrift/tracks/lemans_WIP/objects - this is where the updates go into.
2. data/tracks/lemans_WIP/objects - this is where the original data is expected to be, relative to vdrift.exe

Could you please try to replicate what I did.
1. Download vdrift-2013-06-01.exe. Extract it. It will create a vdrift directory.
2. Copy lemans_WIP into vdrift/data/tracks.
3. Start vdrift/vdrift.exe.