problem with insmod

[Arrigo Benedetti <arrigo@vision.caltech.edu>]

First of all I would like to thank everyone in this list who has 
answered my questions so far, especially Ben...

Now I'm trying to write and and install a kernel module on 2.6, YDL 4.0. 
I compiled the example module by
Alessandro Rubin at http://www.linux.it/~rubini/docs/modules26/src.tar.gz
When I try to load it with insmod I get:

[root@localhost root]#  insmod empty.ko
insmod: error inserting '/home/arrigo/linux/modules/src/empty.ko': -1 
Invalid module format

After some research I found that to load a module on the 2.6 kernel one 
should insmod from module-init-tools 
<ftp://ftp.it.kernel.org/pub/linux/utils/kernel/module-init-tools/>,
not the default insmod from the modutils package that comes with YDL.
So I compile and install module-init-tools, but I get the same error.
Does anyone know what's going on?

Thanks
-Arrigo