Just some guesses:
- Does your modules.dep file correctly contain your module name even after running depmod / rebooting ?
For security reasons (?), depmod can ignore modules that are not owned by root.
It is run also at booting, maybe with a security flag.
- Does your module-init-tools package correctly handle the kernel 2.6 ?
(Probably yes, otherwise you couldn't load a single 2.6 module.)