We've got the updated debs in and the problems is appearing again.  Twice in a couple of days.

Log entry from latest.
[2009/04/02 09:18:12, 0] lib/util_sec.c:set_effective_uid(205)
  setresuid failed with EAGAIN. uid(10000) might be over its NPROC limit
[2009/04/02 09:18:12, 0] lib/util_sec.c:assert_uid(101)
  Failed to set uid privileges to (-1,10000) now set to (0,0)
[2009/04/02 09:18:12, 0] lib/util.c:smb_panic(1633)
  PANIC (pid 7577): failed to set uid

[2009/04/02 09:18:12, 0] lib/util.c:log_stack_trace(1737)
  BACKTRACE: 20 stack frames:
   #0 /usr/sbin/smbd(log_stack_trace+0x1c) [0x613b4c]
   #1 /usr/sbin/smbd(smb_panic+0x43) [0x613c33]
   #2 /usr/sbin/smbd [0x618cf1]
   #3 /usr/sbin/smbd [0x4ba5ae]
   #4 /usr/sbin/smbd(pop_sec_ctx+0x96) [0x4ba726]
   #5 /usr/sbin/smbd(unbecome_root+0x9) [0x4afef9]
   #6 /usr/sbin/smbd(gid_to_sid+0x168) [0x5d36e8]
   #7 /usr/sbin/smbd(get_nt_acl+0x44a) [0x4c435a]
   #8 /usr/sbin/smbd(is_visible_file+0x26e) [0x46e09e]
   #9 /usr/sbin/smbd [0x46e620]
   #10 /usr/sbin/smbd(dptr_ReadDirName+0x54) [0x46e694]
   #11 /usr/sbin/smbd [0x4a54e4]
   #12 /usr/sbin/smbd [0x4a8b13]
   #13 /usr/sbin/smbd(handle_trans2+0x1be) [0x4a92ae]
   #14 /usr/sbin/smbd(reply_trans2+0x6ea) [0x4afc6a]
   #15 /usr/sbin/smbd [0x4c87ce]
   #16 /usr/sbin/smbd(smbd_process+0x7e2) [0x4c9bc2]
   #17 /usr/sbin/smbd(main+0x8cd) [0x6c5fad]
   #18 /lib/libc.so.6(__libc_start_main+0xf4) [0x7fe2ab5d11c4]
   #19 /usr/sbin/smbd [0x45a899]
[2009/04/02 09:18:12, 0] lib/util.c:smb_panic(1638)
  smb_panic(): calling panic action [/usr/share/samba/panic-action 7577]
[2009/04/02 09:18:15, 0] lib/util.c:smb_panic(1646)
  smb_panic(): action returned status 0
[2009/04/02 09:18:15, 0] lib/fault.c:dump_core(181)
  dumping core in /var/log/samba/cores/smbd
[2009/04/02 09:18:15, 1] smbd/service.c:make_connection_snum(1033)
  ldorsett (10.0.0.222) connect to service Admin initially as user ldorsett (uid=10000, gid=1009) (pid 7748)
[2009/04/02 09:18:16, 0] lib/util_sec.c:set_effective_uid(205)
  setresuid failed with EAGAIN. uid(10000) might be over its NPROC limit
[2009/04/02 09:18:16, 0] lib/util_sec.c:assert_uid(101)
  Failed to set uid privileges to (-1,10000) now set to (0,0)
[2009/04/02 09:18:16, 0] lib/util.c:smb_panic(1633)
  PANIC (pid 7748): failed to set uid

[2009/04/02 09:18:16, 0] lib/util.c:log_stack_trace(1737)
  BACKTRACE: 20 stack frames:
   #0 /usr/sbin/smbd(log_stack_trace+0x1c) [0x613b4c]
   #1 /usr/sbin/smbd(smb_panic+0x43) [0x613c33]
   #2 /usr/sbin/smbd [0x618cf1]
   #3 /usr/sbin/smbd [0x4ba5ae]
   #4 /usr/sbin/smbd(pop_sec_ctx+0x96) [0x4ba726]
   #5 /usr/sbin/smbd(unbecome_root+0x9) [0x4afef9]
   #6 /usr/sbin/smbd(gid_to_sid+0x168) [0x5d36e8]
   #7 /usr/sbin/smbd(get_nt_acl+0x44a) [0x4c435a]
   #8 /usr/sbin/smbd(is_visible_file+0x26e) [0x46e09e]
   #9 /usr/sbin/smbd [0x46e620]
   #10 /usr/sbin/smbd(dptr_ReadDirName+0x54) [0x46e694]
   #11 /usr/sbin/smbd [0x4a54e4]
   #12 /usr/sbin/smbd [0x4a8b13]
   #13 /usr/sbin/smbd(handle_trans2+0x1be) [0x4a92ae]
   #14 /usr/sbin/smbd(reply_trans2+0x6ea) [0x4afc6a]
   #15 /usr/sbin/smbd [0x4c87ce]
   #16 /usr/sbin/smbd(smbd_process+0x7e2) [0x4c9bc2]
   #17 /usr/sbin/smbd(main+0x8cd) [0x6c5fad]
   #18 /lib/libc.so.6(__libc_start_main+0xf4) [0x7fe2ab5d11c4]
   #19 /usr/sbin/smbd [0x45a899]
[2009/04/02 09:18:16, 0] lib/util.c:smb_panic(1638)
  smb_panic(): calling panic action [/usr/share/samba/panic-action 7748]
[2009/04/02 09:18:16, 0] lib/util.c:smb_panic(1646)
  smb_panic(): action returned status 0
[2009/04/02 09:18:16, 0] lib/fault.c:dump_core(181)
  dumping core in /var/log/samba/cores/smbd
[2009/04/02 09:18:18, 1] smbd/service.c:make_connection_snum(1033)
  ldorsett (10.0.0.222) connect to service Admin initially as user ldorsett (uid=10000, gid=1009) (pid 7762)
[2009/04/02 09:18:18, 0] lib/util_sec.c:set_effective_uid(205)
  setresuid failed with EAGAIN. uid(10000) might be over its NPROC limit
[2009/04/02 09:18:18, 0] lib/util_sec.c:assert_uid(101)
  Failed to set uid privileges to (-1,10000) now set to (0,0)
[2009/04/02 09:18:18, 0] lib/util.c:smb_panic(1633)
  PANIC (pid 7762): failed to set uid

[2009/04/02 09:18:18, 0] lib/util.c:log_stack_trace(1737)
  BACKTRACE: 20 stack frames:
   #0 /usr/sbin/smbd(log_stack_trace+0x1c) [0x613b4c]
   #1 /usr/sbin/smbd(smb_panic+0x43) [0x613c33]
   #2 /usr/sbin/smbd [0x618cf1]
   #3 /usr/sbin/smbd [0x4ba5ae]
   #4 /usr/sbin/smbd(pop_sec_ctx+0x96) [0x4ba726]
   #5 /usr/sbin/smbd(unbecome_root+0x9) [0x4afef9]
   #6 /usr/sbin/smbd(gid_to_sid+0x168) [0x5d36e8]
   #7 /usr/sbin/smbd(get_nt_acl+0x44a) [0x4c435a]
   #8 /usr/sbin/smbd(is_visible_file+0x26e) [0x46e09e]
   #9 /usr/sbin/smbd [0x46e620]
   #10 /usr/sbin/smbd(dptr_ReadDirName+0x54) [0x46e694]
   #11 /usr/sbin/smbd [0x4a54e4]
   #12 /usr/sbin/smbd [0x4a8b13]
   #13 /usr/sbin/smbd(handle_trans2+0x1be) [0x4a92ae]
   #14 /usr/sbin/smbd(reply_trans2+0x6ea) [0x4afc6a]
   #15 /usr/sbin/smbd [0x4c87ce]
   #16 /usr/sbin/smbd(smbd_process+0x7e2) [0x4c9bc2]
   #17 /usr/sbin/smbd(main+0x8cd) [0x6c5fad]
   #18 /lib/libc.so.6(__libc_start_main+0xf4) [0x7fe2ab5d11c4]
   #19 /usr/sbin/smbd [0x45a899]
[2009/04/02 09:18:18, 0] lib/util.c:smb_panic(1638)
  smb_panic(): calling panic action [/usr/share/samba/panic-action 7762]
[2009/04/02 09:18:18, 0] lib/util.c:smb_panic(1646)
  smb_panic(): action returned status 0
[2009/04/02 09:18:18, 0] lib/fault.c:dump_core(181)
  dumping core in /var/log/samba/cores/smbd
[2009/04/02 09:18:19, 1] smbd/service.c:make_connection_snum(1033)
  ldorsett (10.0.0.222) connect to service Admin initially as user ldorsett (uid=10000, gid=1009) (pid 7776)
[2009/04/02 09:18:19, 0] lib/util_sec.c:set_effective_uid(205)
  setresuid failed with EAGAIN. uid(10000) might be over its NPROC limit
[2009/04/02 09:18:19, 0] lib/util_sec.c:assert_uid(101)
  Failed to set uid privileges to (-1,10000) now set to (0,0)
[2009/04/02 09:18:19, 0] lib/util.c:smb_panic(1633)
  PANIC (pid 7776): failed to set uid

[2009/04/02 09:18:19, 0] lib/util.c:log_stack_trace(1737)
  BACKTRACE: 20 stack frames:
   #0 /usr/sbin/smbd(log_stack_trace+0x1c) [0x613b4c]
   #1 /usr/sbin/smbd(smb_panic+0x43) [0x613c33]
   #2 /usr/sbin/smbd [0x618cf1]
   #3 /usr/sbin/smbd [0x4ba5ae]
   #4 /usr/sbin/smbd(pop_sec_ctx+0x96) [0x4ba726]
   #5 /usr/sbin/smbd(unbecome_root+0x9) [0x4afef9]
   #6 /usr/sbin/smbd(gid_to_sid+0x168) [0x5d36e8]
   #7 /usr/sbin/smbd(get_nt_acl+0x44a) [0x4c435a]
   #8 /usr/sbin/smbd(is_visible_file+0x26e) [0x46e09e]
   #9 /usr/sbin/smbd [0x46e620]
   #10 /usr/sbin/smbd(dptr_ReadDirName+0x54) [0x46e694]
   #11 /usr/sbin/smbd [0x4a54e4]
   #12 /usr/sbin/smbd [0x4a8b13]
   #13 /usr/sbin/smbd(handle_trans2+0x1be) [0x4a92ae]
   #14 /usr/sbin/smbd(reply_trans2+0x6ea) [0x4afc6a]
   #15 /usr/sbin/smbd [0x4c87ce]
   #16 /usr/sbin/smbd(smbd_process+0x7e2) [0x4c9bc2]
   #17 /usr/sbin/smbd(main+0x8cd) [0x6c5fad]
   #18 /lib/libc.so.6(__libc_start_main+0xf4) [0x7fe2ab5d11c4]
   #19 /usr/sbin/smbd [0x45a899]
[2009/04/02 09:18:19, 0] lib/util.c:smb_panic(1638)
  smb_panic(): calling panic action [/usr/share/samba/panic-action 7776]
[2009/04/02 09:18:19, 0] lib/util.c:smb_panic(1646)
  smb_panic(): action returned status 0
[2009/04/02 09:18:19, 0] lib/fault.c:dump_core(181)
  dumping core in /var/log/samba/cores/smbd
[2009/04/02 09:18:20, 1] smbd/service.c:make_connection_snum(1033)
  ldorsett (10.0.0.222) connect to service Admin initially as user ldorsett (uid=10000, gid=1009) (pid 7790)


At this point it succeeds and the user gets a normal connection.