on my machine with two batteries gpm always segfaults when it runs with no power cable plugged in.

24 [lennart@epsilon] ~/projects/systemd (master $)$ lme gdb --args gnome-power-manager 
GNU gdb (GDB) Fedora (7.2.50.20110206-18.fc15)
Copyright (C) 2011 Free Software Foundation, Inc.
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<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /usr/bin/gnome-power-manager...Reading symbols from /usr/lib/debug/usr/bin/gnome-power-manager.debug...done.
done.
(gdb) r
Starting program: /usr/bin/gnome-power-manager 
[Thread debugging using libthread_db enabled]
[New Thread 0x7ffff2138700 (LWP 20656)]
[New Thread 0x7ffff12e6700 (LWP 20657)]
[New Thread 0x7ffff0ae5700 (LWP 20658)]

(gnome-power-manager:20653): GLib-CRITICAL **: g_variant_new_string: assertion `string != NULL' failed

Program received signal SIGSEGV, Segmentation fault.
0x00000038b647cde2 in g_variant_is_trusted (value=0x0) at gvariant-core.c:600
600	  return (value->state & STATE_TRUSTED) != 0;
Missing separate debuginfos, use: debuginfo-install dconf-0.7.2-1.x86_64 expat-2.0.1-10.fc13.x86_64 fontconfig-2.8.0-2.fc14.x86_64 freetype-2.4.4-1.fc15.x86_64 gnome-themes-standard-2.91.8-3.fc15.x86_64 libXau-1.0.6-1.fc14.x86_64 libXcomposite-0.4.3-1.fc15.x86_64 libXcursor-1.1.11-2.fc15.x86_64 libXdamage-1.1.3-1.fc14.x86_64 libXfixes-4.0.5-1.fc14.x86_64 libXi-1.4.1-1.fc15.x86_64 libXinerama-1.1.1-1.fc15.x86_64 libXrender-0.9.6-1.fc14.x86_64 libcroco-0.6.2-5.fc15.x86_64 libogg-1.2.2-2.fc15.x86_64 libpng-1.2.44-2.fc15.x86_64 libtdb-1.2.9-8.fc15.x86_64 libtool-ltdl-2.4-3.fc15.x86_64 libvorbis-1.3.1-2.fc14.x86_64 libxcb-1.7-1.fc15.x86_64 libxml2-2.7.8-4.fc15.x86_64 nss-softokn-freebl-3.12.9-2.fc15.x86_64 pixman-0.20.2-1.fc15.x86_64
(gdb) bt full
#0  0x00000038b647cde2 in g_variant_is_trusted (value=0x0) at gvariant-core.c:600
No locals.
#1  0x00000038b647a416 in g_variant_builder_add_value (builder=0x7fffffffd8b0, value=0x0) at gvariant.c:3079
        __PRETTY_FUNCTION__ = "g_variant_builder_add_value"
#2  0x00000038b647bc5a in g_variant_valist_new (str=0x7fffffffd968, app=0x7fffffffd998) at gvariant.c:4075
        b = {x = {0, 7634624, 0, 0, 0, 18446744073709551615, 7657760, 8, 0, 2, 1033660112, 0, 0, 0, 0, 0}}
        __PRETTY_FUNCTION__ = "g_variant_valist_new"
#3  0x00000038b647bfd7 in g_variant_new_va (format_string=0x41f1dd "usdut)", endptr=0x0, app=0x7fffffffd998) at gvariant.c:4230
        value = <optimized out>
#4  0x00000038b647c0f8 in g_variant_new (format_string=0x41f1db "(susdut)") at gvariant.c:4170
        value = <optimized out>
        ap = {{gp_offset = 16, fp_offset = 48, overflow_arg_area = 0x7fffffffda70, reg_save_area = 0x7fffffffd9b0}}
        __PRETTY_FUNCTION__ = "g_variant_new"
        kind = UP_DEVICE_KIND_BATTERY
        state = UP_DEVICE_STATE_DISCHARGING
        percentage = 98.94722240474259
        time_state = 20303
        time_empty = 20303
        time_full = 0
        value = <optimized out>
        icon = <optimized out>
        device_icon = 0x71a820 ". GThemedIcon gpm-battery-100 battery-full "
#6  0x0000000000410ab8 in gpm_manager_dbus_method_call (connection=<optimized out>, sender=<optimized out>, object_path=<optimized out>, interface_name=<optimized out>, method_name=0x7fffec006760 "GetPrimaryDevice", 
    parameters=<optimized out>, invocation=0x664ea0 [GDBusMethodInvocation], user_data=0x6b6870) at gpm-manager.c:2088
        manager = 0x6b6870 [GpmManager]
        device = <optimized out>
        value = 0x0
        tuple = 0x0
        array = 0x0
        i = <optimized out>
        builder = <optimized out>
#7  0x00000038b7cae81d in call_in_idle_cb (user_data=<optimized out>) at gdbusconnection.c:4424
        invocation = 0x664ea0 [GDBusMethodInvocation]
        vtable = <optimized out>
        registration_id = <optimized out>
        subtree_registration_id = <optimized out>
        __PRETTY_FUNCTION__ = "call_in_idle_cb"
#8  0x00000038b6442b7d in g_main_dispatch (context=0x657270) at gmain.c:2440
        dispatch = 0x38b643eb30 <g_idle_dispatch>
        was_in_call = 0
        user_data = 0x664ea0
        callback = 0x38b7cae6d0 <call_in_idle_cb>
        cb_funcs = 0x38b6715c30
        cb_data = 0x7fffec0080e0
        current_source_link = {data = 0x7fffec002e00, next = 0x0}
        need_destroy = <optimized out>
        source = 0x7fffec002e00
        current = 0x663400
        i = <optimized out>
#9  g_main_context_dispatch (context=0x657270) at gmain.c:3013
No locals.
#10 0x00000038b6443358 in g_main_context_iterate (context=0x657270, block=<optimized out>, dispatch=1, self=<optimized out>) at gmain.c:3091
        max_priority = 0
        timeout = 0
        some_ready = 1
        nfds = 7
        allocated_nfds = <optimized out>
        fds = <optimized out>
#11 0x00000038b644399a in g_main_loop_run (loop=0x6b1b70) at gmain.c:3299
        __PRETTY_FUNCTION__ = "g_main_loop_run"
#12 0x0000000000408476 in main (argc=1, argv=0x7fffffffdef8) at gpm-main.c:304
        system_connection = 0x661840 [GDBusConnection]
        version = 0
        timed_exit = 0
        immediate_exit = 0
        manager = 0x6b6870 [GpmManager]
        error = 0x0
---Type <return> to continue, or q <return> to quit---
        context = 0x638f20
        timer_id = <optimized out>
        options = {{long_name = 0x41e3f5 "version", short_name = 0 '\000', flags = 0, arg = G_OPTION_ARG_NONE, arg_data = 0x7fffffffddd4, description = 0x41e4b8 "Show version of installed program and exit", arg_description = 0x0}, {
            long_name = 0x41e4ab "timed-exit", short_name = 0 '\000', flags = 0, arg = G_OPTION_ARG_NONE, arg_data = 0x7fffffffddd8, description = 0x41e4e8 "Exit after a small delay (for debugging)", arg_description = 0x0}, {long_name = 
    0x41e3fd "immediate-exit", short_name = 0 '\000', flags = 0, arg = G_OPTION_ARG_NONE, arg_data = 0x7fffffffdddc, description = 0x41e518 "Exit after the manager has loaded (for debugging)", arg_description = 0x0}, {long_name = 0x0, 
            short_name = 0 '\000', flags = 0, arg = G_OPTION_ARG_NONE, arg_data = 0x0, description = 0x0, arg_description = 0x0}}
(gdb) 
27 [lennart@epsilon] ~/projects/systemd (master $)$  rpm -qa gnome-power-manager
gnome-power-manager-2.91.5-2.fc15.x86_64