I have the same problem a little time after login my session in Unity.

I note this in my apport log:

ERROR: apport (pid 2272) Tue Sep 25 09:02:13 2012: called for pid 2271, signal 5
ERROR: apport (pid 2272) Tue Sep 25 09:02:13 2012: executable: /usr/lib/dconf/dconf-service (command line "/usr/lib/dconf/dconf-service")
ERROR: apport (pid 2272) Tue Sep 25 09:02:13 2012: gdbus call error: Error: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.SessionManager was not provided by any .service files

ERROR: apport (pid 2272) Tue Sep 25 09:02:13 2012: debug: session gdbus call: 
ERROR: apport (pid 2272) Tue Sep 25 09:02:13 2012: wrote report /var/crash/_usr_lib_dconf_dconf-service.122.crash

And, in the crash report:

ApportVersion: 2.0.1-0ubuntu13
Dependencies:
 coreutils 8.13-3ubuntu3
 debconf 1.5.42ubuntu1
 dpkg 1.16.1.2ubuntu7
 gcc-4.6-base 4.6.3-1ubuntu5
 libacl1 2.2.51-5ubuntu1
 libattr1 1:2.4.46-5ubuntu1
 libbz2-1.0 1.0.6-1
 libc-bin 2.15-0ubuntu10
 libc6 2.15-0ubuntu10
 libdconf0 0.12.0-0ubuntu1.1
 libffi6 3.0.11~rc1-5
 libgcc1 1:4.6.3-1ubuntu5
 libglib2.0-0 2.32.3-0ubuntu1
 liblzma5 5.1.1alpha+20110809-3
 libpcre3 8.12-4
 libselinux1 2.1.0-4.1ubuntu1
 multiarch-support 2.15-0ubuntu10
 perl-base 5.14.2-6ubuntu2.1
 tar 1.26-4ubuntu1
 tzdata 2012e-0ubuntu0.12.04.1
 xz-utils 5.1.1alpha+20110809-3
 zlib1g 1:1.2.3.4.dfsg-3ubuntu4
Disassembly:
 => 0x7fd279e60fdb <g_logv+475>:	lea    0x2a513e(%rip),%rdi        # 0x7fd27a106120
    0x7fd279e60fe2 <g_logv+482>:	mov    %r14d,%esi
    0x7fd279e60fe5 <g_logv+485>:	callq  0x7fd279e95980 <g_private_set>
    0x7fd279e60fea <g_logv+490>:	nopw   0x0(%rax,%rax,1)
    0x7fd279e60ff0 <g_logv+496>:	test   %ebx,%ebx
    0x7fd279e60ff2 <g_logv+498>:	je     0x7fd279e61010 <g_logv+528>
    0x7fd279e60ff4 <g_logv+500>:	sub    $0x1,%ebx
    0x7fd279e60ff7 <g_logv+503>:	bt     %rbx,%r12
    0x7fd279e60ffb <g_logv+507>:	jae    0x7fd279e60ff0 <g_logv+496>
    0x7fd279e60ffd <g_logv+509>:	cmp    $0xffffffff,%ebx
    0x7fd279e61000 <g_logv+512>:	jne    0x7fd279e60e78 <g_logv+120>
    0x7fd279e61006 <g_logv+518>:	nopw   %cs:0x0(%rax,%rax,1)
    0x7fd279e61010 <g_logv+528>:	mov    0x458(%rsp),%rdx
    0x7fd279e61018 <g_logv+536>:	xor    %fs:0x28,%rdx
    0x7fd279e61021 <g_logv+545>:	jne    0x7fd279e6111d <g_logv+797>
    0x7fd279e61027 <g_logv+551>:	add    $0x468,%rsp
InstallationMedia: Ubuntu-Server 10.10 "Maverick Meerkat" - Release amd64 (20101007)
NonfreeKernelModules: nvidia
Package: dconf-service 0.12.0-0ubuntu1.1
PackageArchitecture: amd64
ProcVersionSignature: Ubuntu 3.2.0-31.50-generic 3.2.28
Registers:
 rax            0x0	0
 rbx            0x2	2
 rcx            0x7fd279bee750	140541962413904
 rdx            0x1	1
 rsi            0xffffffff	4294967295
 rdi            0x7fd279bee720	140541962413856
 rbp            0x2	0x2
 rsp            0x7fff5b740280	0x7fff5b740280
 r8             0x0	0
 r9             0x0	0
 r10            0x0	0
 r11            0x246	582
 r12            0x4	4
 r13            0x7fff5b740728	140734727718696
 r14            0x0	0
 r15            0x0	0
 rip            0x7fd279e60fdb	0x7fd279e60fdb <g_logv+475>
 eflags         0x246	[ PF ZF IF ]
 cs             0x33	51
 ss             0x2b	43
 ds             0x0	0
 es             0x0	0
 fs             0x0	0
 gs             0x0	0
SourcePackage: d-conf
Stacktrace:
 #0  0x00007fd279e60fdb in g_logv () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
 No symbol table info available.
 #1  0x00007fd279e611b2 in g_log () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
 No symbol table info available.
 #2  0x0000000000404e50 in ?? ()
 No symbol table info available.
 #3  0x0000000000402f38 in ?? ()
 No symbol table info available.
 #4  0x00007fd27985976d in __libc_start_main (main=0x402f20, argc=1, ubp_av=0x7fff5b740978, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff5b740968) at libc-start.c:226
         result = <optimized out>
         unwind_buf = {cancel_jmp_buf = {{jmp_buf = {0, 8280920172592276728, 4206528, 140734727719280, 0, 0, -8280699223994096392, -8264300964955380488}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x405b10, 0x7fff5b740978}, data = {prev = 0x0, cleanup = 0x0, canceltype = 4217616}}}
         not_first_call = <optimized out>
 #5  0x0000000000402fe9 in ?? ()
 No symbol table info available.
 #6  0x00007fff5b740968 in ?? ()
 No symbol table info available.
 #7  0x000000000000001c in ?? ()
 No symbol table info available.
 #8  0x0000000000000001 in ?? ()
 No symbol table info available.
 #9  0x00007fff5b741d19 in ?? ()
 No symbol table info available.
 #10 0x0000000000000000 in ?? ()
 No symbol table info available.
StacktraceTop:
 ?? ()
 ?? ()
 __libc_start_main (main=0x402f20, argc=1, ubp_av=0x7fff5b740978, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff5b740968) at libc-start.c:226
 ?? ()
 ?? ()
Tags:  precise
ThreadStacktrace:
 .
 Thread 1 (Thread 0x7fd27a8967c0 (LWP 2271)):
 #0  0x00007fd279e60fdb in g_logv () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
 No symbol table info available.
 #1  0x00007fd279e611b2 in g_log () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
 No symbol table info available.
 #2  0x0000000000404e50 in ?? ()
 No symbol table info available.
 #3  0x0000000000402f38 in ?? ()
 No symbol table info available.
 #4  0x00007fd27985976d in __libc_start_main (main=0x402f20, argc=1, ubp_av=0x7fff5b740978, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff5b740968) at libc-start.c:226
         result = <optimized out>
         unwind_buf = {cancel_jmp_buf = {{jmp_buf = {0, 8280920172592276728, 4206528, 140734727719280, 0, 0, -8280699223994096392, -8264300964955380488}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x405b10, 0x7fff5b740978}, data = {prev = 0x0, cleanup = 0x0, canceltype = 4217616}}}
         not_first_call = <optimized out>
 #5  0x0000000000402fe9 in ?? ()
 No symbol table info available.
 #6  0x00007fff5b740968 in ?? ()
 No symbol table info available.
 #7  0x000000000000001c in ?? ()
 No symbol table info available.
 #8  0x0000000000000001 in ?? ()
 No symbol table info available.
 #9  0x00007fff5b741d19 in ?? ()
 No symbol table info available.
 #10 0x0000000000000000 in ?? ()
 No symbol table info available.
Title: dconf-service crashed with signal 5 in __libc_start_main()
UpgradeStatus: Upgraded to precise on 2012-03-23 (185 days ago)