Weird errors for loading modules

hi
i recently comiled 2.5.69 kernel and all goes fine, except that i'm not able to load modules at startup. The error it gives is like: "modprobe: ERROR module xyz doesn't exist in /proc/modules". The same error comes out when i try to load modules as root, but all goes fine if i log in as normal user and then i issue 'sudo modprobe xyz'. That's a strange behaviour, anyone knows what can cause it?
I use module-init-tools 0.9.11

Thanks,

Daniele Pala