This doesn't look related to the other 2.6.39.4 threads (that seem to be all solely build-related). I get this during boot on a 64-bit Debian Squeeze. 2.6.39.3 boots just fine. it's slightly garbled at the beginning, but I figured the context was important enough to leave it untouched. If there's anything helpful I should send along, I'll do so immediately. If it'd also be helpful, I can use 2.6.39.3's version of check_kill_permission in 2.6.39.4, if you don't think it'd cause additional issues. Thanks!
[ 19.215388] BUG: unable to handle kernel cripts/local-preNULL pointer dereference at 0000000000000008
[ 19.225066] IP: [<ffffffff8106230b>] check_kill_permission+0xdb/0x1e0
Begin: Running [ 19.225066] PGD 12c7e2067 /scripts/local-bPUD 0 ottom ... done.
done.
Begin: R[ 19.225066] Oops: 0000 [#1] unning /scripts/SMP
init-bottom ... [ 19.225066] last sysfs file: /sys/kernel/uevent_seqnum
[ 19.225066] CPU 2
[ 19.225066] Modules linked in: sg sr_mod uhci_hcd cdrom sd_mod ehci_hcd crc_t10dif [last unloaded: scsi_wait_scan]
[ 19.225066]
[ 19.225066] Pid: 927, comm: udevd Not tainted 2.6.39.4 #1 Dell Inc. PowerEdge 1950/0DT097
[ 19.225066] RIP: 0010:[<ffffffff8106230b>] [<ffffffff8106230b>] check_kill_permission+0xdb/0x1e0
[ 19.225066] RSP: 0018:ffff88012c097e38 EFLAGS: 00010046
[ 19.225066] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88012f32b600
[ 19.225066] RDX: ffff88012f32e780 RSI: 0000000000000000 RDI: ffffffff81aa8b80
[ 19.225066] RBP: ffff88012c097e58 R08: 0000000000000000 R09: 0000000000000001
[ 19.225066] R10: 0000000000000000 R11: 0000000000000001 R12: ffff88012f345dc0
[ 19.225066] R13: 000000000000000f R14: ffff88012f345dc0 R15: ffff88012f346078
[ 19.225066] FS: 0000000000000000(0000) GS:ffff88012fc80000(0000) knlGS:0000000000000000
[ 19.225066] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 19.225066] CR2: 0000000000000008 CR3: 0000000001693000 CR4: 00000000000006f0
[ 19.225066] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 19.225066] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 19.225066] Process udevd (pid: 927, threadinfo ffff88012cbf33d8, task ffff88012cbf2ee0)
[ 19.225066] Stack:
[ 19.225066] 0000000000000000 ffff88012f345dc0 0000000000000000 000000000000000f
[ 19.225066] ffff88012c097e88 ffffffff81063a3e ffff88012f345dc0 ffff88012f345dc0
[ 19.225066] ffff88012cbf2ee0 ffff88012f0b8000 ffff88012c097f18 ffffffff81051c23
[ 19.225066] Call Trace:
[ 19.225066] [<ffffffff81063a3e>] group_send_sig_info+0x2e/0x90
[ 19.225066] [<ffffffff81051c23>] do_exit+0x313/0x8e0
[ 19.225066] [<ffffffff812f92aa>] ? trace_hardirqs_off_thunk+0x3a/0x6c
[ 19.225066] [<ffffffff8105223c>] do_group_exit+0x4c/0xc0
[ 19.225066] [<ffffffff810522c7>] sys_exit_group+0x17/0x20
[ 19.225066] [<ffffffff81665674>] system_call_fastpath+0x16/0x1b
[ 19.225066] Code: 8b 94 24 30 06 00 00 48 8b 42 68 48 8b 78 70 48 8b 41 68 48 39 78 70 0f 84 d3 00 00 00 be 05 00 00 00 e8 29 80 ff ff 84 c0 74 55
[ 19.225066] 7b 08 fa 90 0f 84 8a 00 00 00 44 89 ee 4c 89 e7 e8 ff cd 27
[ 19.225066] RIP [<ffffffff8106230b>] check_kill_permission+0xdb/0x1e0
[ 19.225066] RSP <ffff88012c097e38>
[ 19.225066] CR2: 0000000000000008
[ 19.225066] ---[ end trace 3806bcd0b6ff38d7 ]---
[ 19.225066] Fixing recursive fault but reboot is needed!