This is actually a FAQ at sourceforge and I have read and tried the various things to fix it and I am lost. This is what they say:
# The kernel running should have been compiled from the same sources as ndiswrapper is.
# The compiler used for compiling kernel should be same as the one used to compile ndiswrapper. To make sure these conditions are met, run cat /proc/version and modinfo ndiswrapper and make sure that they match both compiler and kernel versions

When I do that this is what I get:

[root@localhost ~]# cat /proc/version
Linux version 2.6.18-1.2849.fc6 ( (gcc version 4.1.1 20061011 (Red Hat 4.1.1-30)) #1 SMP Fri Nov 10 12:36:14 EST 2006
[root@localhost ~]# modinfo ndiswrapper
filename: /lib/modules/2.6.18-1.2849.fc6/extra/ndiswrapper/ndiswrapper.ko
license: GPL
version: 1.25
description: NDIS wrapper driver
author: ndiswrapper team <>
srcversion: A5FD8EBF8CE70C18EE9BAD0
vermagic: 2.6.18-1.2849.fc6 SMP mod_unload 686 REGPARM 4KSTACKS gcc-4.1
parm: if_name:Network interface name or template (default: wlan%d) (charp)
parm: proc_uid:The uid of the files created in /proc (default: 0). (int)
parm: proc_gid:The gid of the files created in /proc (default: 0). (int)
parm: debug:debug level (int)
parm: hangcheck_interval:The interval, in seconds, for checking if driver is hung. (default: 0) (int)
[root@localhost ~]#

It seems to match to me. Any suggestions? I have been trying to get my wireless adapter to work for days.