Compiling the kernel with Suse's default settings works perfect. But when I use
my custom .config files (based on Suse's default settings) then I get the
following error:
 CC [M]  net/netfilter/nf_conntrack_core.o
net/netfilter/nf_conntrack_core.c: In function ‘nf_conntrack_in’:
net/netfilter/nf_conntrack_core.c:854: warning: ‘set_reply’ may be used
uninitialized in this function
  CC [M]  net/netfilter/nf_conntrack_standalone.o
  CC [M]  net/netfilter/nf_conntrack_l3proto_generic.o
  CC [M]  net/netfilter/nf_conntrack_proto_generic.o
  CC [M]  net/netfilter/nf_conntrack_proto_tcp.o
  CC [M]  net/netfilter/nf_conntrack_proto_udp.o
net/netfilter/nf_conntrack_proto_udp.c: In function ‘csum6’:
net/netfilter/nf_conntrack_proto_udp.c:158: error: dereferencing pointer to
incomplete type
net/netfilter/nf_conntrack_proto_udp.c:158: error: dereferencing pointer to
incomplete type
make[2]: *** [net/netfilter/nf_conntrack_proto_udp.o] Fehler 1
make[1]: *** [net/netfilter] Fehler 2
make: *** [net] Fehler 2

Only thing I changed in the .config is (IIRC)
-removed _lots_ of stuff
-optimized for Pentium M

When you fix it please also post the patch here, since downloading 40MB via ISDN
is no fun.