The same symptoms occur here on a setup where 
* samba 3.0.28a-1ubuntu4.7
* winbind 3.0.28a-1ubuntu4.7
is authenticating against a W2K3-Server.

The server is running hardy without any custom modifications.



[Thread debugging using libthread_db enabled]
[New Thread 0xb7ade6d0 (LWP 10153)]
0xb7ef4410 in __kernel_vsyscall ()
#0  0xb7ef4410 in __kernel_vsyscall ()
#1  0xb7c9d4d3 in waitpid () from /lib/tls/i686/cmov/libc.so.6
#2  0xb7c40643 in ?? () from /lib/tls/i686/cmov/libc.so.6
#3  0x08123178 in smb_panic (why=0x8276ea4 "internal error") at lib/util.c:1639
#4  0x0810d99a in sig_fault (sig=6) at lib/fault.c:47
#5  <signal handler called>
#6  0xb7ef4410 in __kernel_vsyscall ()
#7  0xb7c33085 in raise () from /lib/tls/i686/cmov/libc.so.6
#8  0xb7c34a01 in abort () from /lib/tls/i686/cmov/libc.so.6
#9  0xb7c2c10e in __assert_fail () from /lib/tls/i686/cmov/libc.so.6
#10 0xb7d73bea in ldap_parse_result () from /usr/lib/libldap_r-2.4.so.2
#11 0x08239e4c in ads_do_paged_search_args (ads=0x8380e00, 
   bind_path=<value optimized out>, scope=0, 
   expr=0x8265735 "(objectclass=*)", attrs=0xbf970470, args=0x0, 
   res=0xbf970478, count=0xbf970394, cookie=0xbf970398) at libads/ldap.c:700
#12 0x0823a1cf in ads_do_search_all_args (ads=0x8380e00, 
   bind_path=0x832ef80 "", scope=0, expr=0x8265735 "(objectclass=*)", 
   attrs=0xbf970470, args=0x0, res=0xbf970478) at libads/ldap.c:772
#13 0x08243769 in ads_do_search_retry_internal (ads=0x8380e00, 
   bind_path=0x82aa7b5 "", scope=0, expr=0x8265735 "(objectclass=*)", 
   attrs=0xbf970470, args=0x0, res=0xbf970478) at libads/ldap_utils.c:60
#14 0x08243cda in ads_do_search_retry (ads=0x8380e00, bind_path=0x82aa7b5 "", 
   scope=0, expr=0x8265735 "(objectclass=*)", attrs=0xbf970470, 
   res=0xbf970478) at libads/ldap_utils.c:124
#15 0x08236ccc in ads_USN (ads=0x8380e00, usn=0x832ea44) at libads/ldap.c:2328
#16 0x080b4289 in sequence_number (domain=0x832e5c0, seq=0x832ea44)
   at nsswitch/winbindd_ads.c:1021
#17 0x08098a51 in refresh_sequence_number (domain=0x832e5c0, 
   force=<value optimized out>) at nsswitch/winbindd_cache.c:479
#18 0x08099079 in wcache_fetch (cache=0x832e4f8, domain=0x832e5c0, 
   format=0x826065d "NS/%s/%s") at nsswitch/winbindd_cache.c:601
#19 0x0809b6dd in name_to_sid (domain=0x832e5c0, mem_ctx=0x82d0eb8, 
   domain_name=0xbf970ae4 "REDACTED", name=0xbf970be4 "REMOVED", sid=0xbf970834, 
   type=0xbf970878) at nsswitch/winbindd_cache.c:1358
#20 0x08094311 in winbindd_lookup_sid_by_name (mem_ctx=0x82d0eb8, 
   domain=0x832e5c0, domain_name=0xbf970ae4 "REDACTED", 
   name=0xbf970be4 "lantzen", sid=0xbf970834, type=0xbf970878)
   at nsswitch/winbindd_util.c:707
#21 0x080bdc78 in winbindd_dual_lookupname (domain=0x832e5c0, state=0xbf970988)
   at nsswitch/winbindd_async.c:953
#22 0x080b943f in schedule_async_request (child=0x832ea98)
   at nsswitch/winbindd_dual.c:481
#23 0x080ba33f in async_request_fail (state=0x83570c8)
   at nsswitch/winbindd_dual.c:208
#24 0x0808b9da in rw_callback (event=0x832eea8, flags=1)
   at nsswitch/winbindd.c:389
#25 0x0808c3f9 in main (argc=) at nsswitch/winbindd.c:835
The program is running.  Quit anyway (and detach it)? (y or n) [answered Y; input not from terminal]