unresolved symbols with 2.6.3 (read the FAQ)

Greetings! I'm running the 2.6.3 kernel on a Redhat 8.1 (IIRC) system and just
tried to get yesterday's cvs snapshot to work with an SMC2662W adapter. What
happens, when I try to load the driver:

--
[root@junkie root]# modprobe -v at76c503-rfmd
insmod /lib/modules/2.6.3/kernel/drivers/usb/at76c503.ko 
WARNING: Error inserting at76c503 (/lib/modules/2.6.3/kernel/drivers/usb/at76c503.ko): Unknown symbol in module, or unknown parameter (see dmesg)
insmod /lib/modules/2.6.3/kernel/drivers/usb/at76c503-rfmd.ko 
FATAL: Error inserting at76c503_rfmd (/lib/modules/2.6.3/kernel/drivers/usb/at76c503-rfmd.ko): Unknown symbol in module, or unknown parameter (see dmesg)
--

The output from dmesg is:

--
/usr/src/at76c503a/usbdfu.c: USB Device Firmware Upgrade (DFU) handler v0.12beta11 loading
at76c503: Unknown symbol iw_handler_set_spy
at76c503: Unknown symbol iw_handler_get_thrspy
at76c503: Unknown symbol iw_handler_get_spy
at76c503: Unknown symbol wireless_spy_update
at76c503: Unknown symbol iw_handler_set_thrspy
at76c503_rfmd: Unknown symbol at76c503_delete_device
at76c503_rfmd: Unknown symbol at76c503_do_probe
--

lsmod shows that only the first module got loaded:

--
[root@junkie at76c503a]# lsmod
Module                  Size  Used by
usbdfu                  4708  0
--

Kernel configuration and running kernel are definitely matching. I
edited the Makefile to point to /usr/src/linux where the sources of the
running kernel are located.

I can't do

grep alloc_skb /proc/ksyms

as suggested in a thread mentioned in the Troubleshooting section,
because with my 2.6.3 kernel, there is no /proc/ksyms.

How to further narrow down the problem? Would it make sense to try a
newer 2.6 kernel source tree?

Regards, Frank