This is a semi-automatic report based on the latest archive rebuild results [1].
Apologies if it reaches you in error.
Excerpt from the buildlog:
gcc -DHAVE_CONFIG_H -I. -I.. -I/usr/include -I../libloqui -I../libloqui -I.. -I.. -DG_LOG_DOMAIN=\"Loqui\" -pthread -I/usr/include/gtk-2.0 -I/usr/lib/i386-linux-gnu/gtk-2.0/include -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/pango-1.0 -I/usr/include/gio-unix-2.0/ -I/usr/include/glib-2.0 -I/usr/lib/i386-linux-gnu/glib-2.0/include -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng12 -g -DDATADIR=\""/usr/share"\" -Wall -Wredundant-decls -Wmissing-declarations -Wmissing-prototypes -g -O2 -fPIE -fstack-protector --param=ssp-buffer-size=4 -Wformat -Wformat-security -Werror=format-security -c loqui-tray-icon.c
gcc -DHAVE_CONFIG_H -I. -I.. -I/usr/include -I../libloqui -I../libloqui -I.. -I.. -DG_LOG_DOMAIN=\"Loqui\" -pthread -I/usr/include/gtk-2.0 -I/usr/lib/i386-linux-gnu/gtk-2.0/include -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/pango-1.0 -I/usr/include/gio-unix-2.0/ -I/usr/include/glib-2.0 -I/usr/lib/i386-linux-gnu/glib-2.0/include -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng12 -g -DDATADIR=\""/usr/share"\" -Wall -Wredundant-decls -Wmissing-declarations -Wmissing-prototypes -g -O2 -fPIE -fstack-protector --param=ssp-buffer-size=4 -Wformat -Wformat-security -Werror=format-security -c loqui-channel-entry-action-group.c
gcc -DHAVE_CONFIG_H -I. -I.. -I/usr/include -I../libloqui -I../libloqui -I.. -I.. -DG_LOG_DOMAIN=\"Loqui\" -pthread -I/usr/include/gtk-2.0 -I/usr/lib/i386-linux-gnu/gtk-2.0/include -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/pango-1.0 -I/usr/include/gio-unix-2.0/ -I/usr/include/glib-2.0 -I/usr/lib/i386-linux-gnu/glib-2.0/include -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng12 -g -DDATADIR=\""/usr/share"\" -Wall -Wredundant-decls -Wmissing-declarations -Wmissing-prototypes -g -O2 -fPIE -fstack-protector --param=ssp-buffer-size=4 -Wformat -Wformat-security -Werror=format-security -c loqui-channel-entry-ui-data.c
gcc -DHAVE_CONFIG_H -I. -I.. -I/usr/include -I../libloqui -I../libloqui -I.. -I.. -DG_LOG_DOMAIN=\"Loqui\" -pthread -I/usr/include/gtk-2.0 -I/usr/lib/i386-linux-gnu/gtk-2.0/include -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/pango-1.0 -I/usr/include/gio-unix-2.0/ -I/usr/include/glib-2.0 -I/usr/lib/i386-linux-gnu/glib-2.0/include -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng12 -g -DDATADIR=\""/usr/share"\" -Wall -Wredundant-decls -Wmissing-declarations -Wmissing-prototypes -g -O2 -fPIE -fstack-protector --param=ssp-buffer-size=4 -Wformat -Wformat-security -Werror=format-security -c loqui-channel-entry-action-group-ui.c
gcc -DHAVE_CONFIG_H -I. -I.. -I/usr/include -I../libloqui -I../libloqui -I.. -I.. -DG_LOG_DOMAIN=\"Loqui\" -pthread -I/usr/include/gtk-2.0 -I/usr/lib/i386-linux-gnu/gtk-2.0/include -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/pango-1.0 -I/usr/include/gio-unix-2.0/ -I/usr/include/glib-2.0 -I/usr/lib/i386-linux-gnu/glib-2.0/include -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng12 -g -DDATADIR=\""/usr/share"\" -Wall -Wredundant-decls -Wmissing-declarations -Wmissing-prototypes -g -O2 -fPIE -fstack-protector --param=ssp-buffer-size=4 -Wformat -Wformat-security -Werror=format-security -c loqui-notifier-gtk.c
/bin/bash ../libtool --tag=CC --mode=link gcc -g -O2 -fPIE -fstack-protector --param=ssp-buffer-size=4 -Wformat -Wformat-security -Werror=format-security -Wl,-Bsymbolic-functions -fPIE -pie -Wl,-z,relro -Wl,-z,now -o loqui gtkutils.o main.o loqui_app_actions.o loqui_stock.o loqui_app.o loqui_app_info.o loqui_channel_entry_store.o loqui_channel_entry_action.o loqui_channel_buffer_gtk.o loqui_dropdown_box.o loqui_account_manager_store.o channel_tree.o nick_list.o about.o account_list_dialog.o loqui_statusbar.o prefs_dialog.o loqui_channel_text_view.o command_dialog.o remark_entry.o loqui_channelbar.o loqui_select_dialog.o prefs_general_upgrader.o loqui-core-gtk.o loqui-style-entry.o loqui-account-dialog.o loqui-protocol-selection-dialog.o loqui-transfer-window.o loqui-tray-icon.o loqui-channel-entry-action-group.o loqui-channel-entry-ui-data.o loqui-channel-entry-action-group-ui.o loqui-notifier-gtk.o -pthread -lgtk-x11-2.0 -lgdk-x11-2.0 -latk-1.0 -lgio-2.0 -lpangoft2-1.0 -lpangocairo-1.0 -lgdk_pixbuf-2.0 -lcairo -lpango-1.0 -lfreetype -lfontconfig -lgobject-2.0 -lgmodule-2.0 -lgthread-2.0 -lrt -lglib-2.0 ../libloqui/libloqui.la
libtool: link: gcc -g -O2 -fPIE -fstack-protector --param=ssp-buffer-size=4 -Wformat -Wformat-security -Werror=format-security -Wl,-Bsymbolic-functions -fPIE -pie -Wl,-z -Wl,relro -Wl,-z -Wl,now -o loqui gtkutils.o main.o loqui_app_actions.o loqui_stock.o loqui_app.o loqui_app_info.o loqui_channel_entry_store.o loqui_channel_entry_action.o loqui_channel_buffer_gtk.o loqui_dropdown_box.o loqui_account_manager_store.o channel_tree.o nick_list.o about.o account_list_dialog.o loqui_statusbar.o prefs_dialog.o loqui_channel_text_view.o command_dialog.o remark_entry.o loqui_channelbar.o loqui_select_dialog.o prefs_general_upgrader.o loqui-core-gtk.o loqui-style-entry.o loqui-account-dialog.o loqui-protocol-selection-dialog.o loqui-transfer-window.o loqui-tray-icon.o loqui-channel-entry-action-group.o loqui-channel-entry-ui-data.o loqui-channel-entry-action-group-ui.o loqui-notifier-gtk.o -pthread -lgtk-x11-2.0 -lgdk-x11-2.0 -latk-1.0 -lpangoft2-1.0 -lpangocairo-1.0 -lgdk_pixbuf-2.0 /usr/lib/i386-linux-gnu/libcairo.so -lpango-1.0 /usr/lib/i386-linux-gnu/libfreetype.so -lfontconfig -lgmodule-2.0 -lgthread-2.0 -lrt ../libloqui/.libs/libloqui.a -lgio-2.0 -lgobject-2.0 -lglib-2.0 -pthread
../libloqui/.libs/libloqui.a(loqui-core.o): In function `___real_loqui_core_initialize':
/build/buildd/loqui-0.5.2/libloqui/loqui-core.gob:58: undefined reference to `g_thread_init'
collect2: ld returned 1 exit status
make[5]: *** [loqui] Error 1
make[5]: Leaving directory `/build/buildd/loqui-0.5.2/src'
make[4]: *** [all-recursive] Error 1
make[4]: Leaving directory `/build/buildd/loqui-0.5.2/src'
make[3]: *** [all] Error 2
make[3]: Leaving directory `/build/buildd/loqui-0.5.2/src'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory `/build/buildd/loqui-0.5.2'
make[1]: *** [all] Error 2
make[1]: Leaving directory `/build/buildd/loqui-0.5.2'
dh_auto_build: make -j1 returned exit code 2
make: *** [build] Error 2
dpkg-buildpackage: error: debian/rules build gave error exit status 2
******************************************************************************
Build finished at 20120208-0814
FAILED [dpkg-buildpackage died]
The full buidlog can be found at https://launchpad.net/ubuntu/+archive/test-rebuild-20120201/+build/3160814/+files/buildlog_ubuntu-precise-i386.loqui_0.5.2-1_FAILEDTOBUILD.txt.gz.
[1] http://people.ubuntuwire.org/~wgrant/rebuild-ftbfs-test/test-rebuild-20120201-precise.html
This bug was fixed in the package loqui - 0.5.2-1ubuntu1
---------------
loqui (0.5.2-1ubuntu1) precise; urgency=low
* Only call g_thread_init when building against glib <2.31.0 (LP: #935284)
-- Andreas Moog <email address hidden> Mon, 27 Feb 2012 21:41:23 +0100