When I do "service iptables restart" (or "service iptables start") I get
following output

Flushing firewall rules:                                   [  OK  ]
Setting chains to policy ACCEPT: filter                    [  OK  ]
Unloading iptables modules:

After which it sits there forever. "ps" shows that it's doing "modprobe -r
ip_conntrack_ftp". "lsmod" shows that it succeeds in unloading the module, or at
least in removing it from lsmod's listing. No error messages appear in the
syslog. Control-C doesn't kill the modprobe process, nor does even sending it
SIGKILL.

This didn't happen before I had updated to iptables-1.2.8-8.72.3. Kernel is
kernel-2.4.20-20.7. If I run the command immediately after booting the box, it
works alright, but fails repeatably when the box has been running for a while.

If, while the modprobe -r is still running, I do "insmod ip_conntrack_ftp", I
get the following errors:

/lib/modules/2.4.20-20.7/kernel/net/ipv4/netfilter/ip_conntrack_ftp.o:
unresolved symbol ip_conntrack_helper_unregister_Reea5a3fd
/lib/modules/2.4.20-20.7/kernel/net/ipv4/netfilter/ip_conntrack_ftp.o:
unresolved symbol ip_conntrack_helper_register_Ra22d6eb5
/lib/modules/2.4.20-20.7/kernel/net/ipv4/netfilter/ip_conntrack_ftp.o:
unresolved symbol ip_conntrack_expect_related_Rfc718b15