module unresolved symbols

Hi all, kindly redirect me if this is the wrong list.

Starting with a stock RH 7.0 install, I changed a single kernel config
item and recompiled with 'make defs clean bzImage modules
modules_install'.

Booted on the new kernel and depmod complains that dozens of modules
contain unresolved symbols. Back to the original kernel, now it also
complains of unresolved symbols (not the same set of modules, and modules
that were previously OK).

I can't find an answer on the net, does anyone know how to fix this?

Thanks == Rich