As requested, I'm appending the Valgrind log. Crash ocurred while still choosing File -> Exit on Rhythmbox's menu; I never got the chance to actually press Exit.

Console output:
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ubuntu@lucid_amd64:~$ G_SLICE=always-malloc G_DEBUG=gc-friendly  valgrind -v --tool=memcheck --leak-check=full --num-callers=40 --log-file=valgrind.log /usr/bin/rhythmbox

(rhythmbox:21656): Rhythmbox-WARNING **: Could not open device /dev/radio0
** (rhythmbox:21656): DEBUG: Loading the real store page

** (rhythmbox:21656): WARNING **: Error calling current_status: Message did not receive a reply (timeout by message bus)

** (rhythmbox:21656): WARNING **: Could not connect to Ubuntu One: Message did not receive a reply (timeout by message bus)

liboauth: data to sign='GET&https%3A%2F%2Fone.ubuntu.com%2Fmusic%2Flogin&oauth_callback%3DNone%26oauth_consumer_key%3Dubuntuone%26oauth_nonce%3DXXXXXXXXXXXXXXXXXXXXXXXXXXXX%26oauth_signature_method%3DHMAC-SHA1%26oauth_timestamp%3DXXXXXXXXXX%26oauth_token%3DXXXXXXXXXXXXXXXXXXXX%26oauth_verifier%3DNone%26oauth_version%3D1.0'


liboauth: key='hammertime&XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'

** (rhythmbox:21656): DEBUG: navigation requested to https://one.ubuntu.com/music/login?oauth_callback=None&oauth_consumer_key=ubuntuone&oauth_nonce=XXXXXXXXXXXXXXXXXXXXXXXXXXXX&oauth_signature_method=HMAC-SHA1&oauth_timestamp=XXXXXXXXXX&oauth_token=XXXXXXXXXXXXXXXXXXXX&oauth_verifier=None&oauth_version=1.0&oauth_signature=XXXXXXXXXXXXXXXXXXXXXXXXXXX%3D

(rhythmbox:21656): GLib-GObject-WARNING **: instance with invalid (NULL) class pointer

(rhythmbox:21656): GLib-GObject-CRITICAL **: g_signal_handlers_unblock_matched: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed

(rhythmbox:21656): GLib-GObject-WARNING **: instance with invalid (NULL) class pointer

(rhythmbox:21656): GLib-GObject-CRITICAL **: g_signal_handlers_unblock_matched: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed

(rhythmbox:21656): Rhythmbox-CRITICAL **: rb_property_view_set_selection: assertion `RB_IS_PROPERTY_VIEW (view)' failed

(rhythmbox:21656): GLib-GObject-WARNING **: instance with invalid (NULL) class pointer

(rhythmbox:21656): GLib-GObject-CRITICAL **: g_signal_handlers_unblock_matched: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed

(rhythmbox:21656): GLib-GObject-WARNING **: instance with invalid (NULL) class pointer

(rhythmbox:21656): GLib-GObject-CRITICAL **: g_signal_handlers_unblock_matched: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed

(rhythmbox:21656): Rhythmbox-CRITICAL **: rb_property_view_set_selection: assertion `RB_IS_PROPERTY_VIEW (view)' failed

(rhythmbox:21656): GLib-GObject-WARNING **: instance with invalid (NULL) class pointer

(rhythmbox:21656): GLib-GObject-CRITICAL **: g_signal_handlers_unblock_matched: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed

(rhythmbox:21656): GLib-GObject-WARNING **: instance with invalid (NULL) class pointer

(rhythmbox:21656): GLib-GObject-CRITICAL **: g_signal_handlers_unblock_matched: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed

(rhythmbox:21656): Rhythmbox-CRITICAL **: rb_property_view_set_selection: assertion `RB_IS_PROPERTY_VIEW (view)' failed
Morto
ubuntu@lucid_amd64:~$ dir valgrind.log 
-rw------- 1 ubuntu ubuntu 8,6M 2011-12-01 22:30 valgrind.log

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