I am not planning to recompile the kernel again because I remember I did few months ago recompiled the 2.4.20 kernel with hostap 0.3.9 for SharpROM and the kernel crash like you did.
I ported the OZ's hostap driver over (v0.3.9) and it still give me the same errror.
give the CFLAGS a try, let me know if its work or not.
Thanks,