firefox crashes after a few minuts and cannot find any web, even in local. just keeps thinking. Cannot be closed, must to be killed

Binary package hint: firefox-3.5

firefox crashes after a few minuts and cannot find any web, even in local. just keeps thinking. But didn't find nothing a no error appears.
Cannot be closed and the process must to be killed.

ProblemType: Bug
Architecture: amd64
CheckboxSubmission: 7012a2808ac85d8a16fccb017e62346a
CheckboxSystem: daed2f3d6643b4a84b4520a2427f8c2b
Date: Tue Nov 17 21:41:33 2009
DistroRelease: Ubuntu 9.10
NonfreeKernelModules: nvidia
Package: firefox-3.5 3.5.5+nobinonly-0ubuntu0.9.10.1
ProcEnviron:
 LANGUAGE=ca_ES.UTF-8
 LANG=ca_ES.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-14.48-generic
SourcePackage: firefox-3.5
Uname: Linux 2.6.31-14-generic x86_64
XsessionErrors:
 (gnome-settings-daemon:2552): GLib-CRITICAL **: g_propagate_error: assertion `src != NULL' failed
 (gnome-settings-daemon:2552): GLib-CRITICAL **: g_propagate_error: assertion `src != NULL' failed
 (nautilus:2655): Eel-CRITICAL **: eel_preferences_get_boolean: assertion `preferences_is_initialized ()' failed
 (polkit-gnome-authentication-agent-1:2694): GLib-CRITICAL **: g_once_init_leave: assertion `initialization_value != 0' failed
 (gnome-panel:2654): Gdk-WARNING **: /build/buildd/gtk+2.0-2.18.3/gdk/x11/gdkdrawable-x11.c:952 drawable is not a pixmap or window