[rocketmouse@archlinux ~]$ firefox -safe-mode (process:30167): GLib-CRITICAL **: g_slice_set_config: assertion 'sys_page_size == 0' failed [rocketmouse@archlinux ~]$ firefox -safe-mode -new-instance (process:30171): GLib-CRITICAL **: g_slice_set_config: assertion 'sys_page_size == 0' failed [rocketmouse@archlinux ~]$ killall firefox After killall I still get the warning, but firefox does work again :) [rocketmouse@archlinux ~]$ firefox -safe-mode -new-instance (process:30197): GLib-CRITICAL **: g_slice_set_config: assertion 'sys_page_size == 0' failed [rocketmouse@archlinux ~]$ firefox (process:30256): GLib-CRITICAL **: g_slice_set_config: assertion 'sys_page_size == 0' failed Sorry for the noise, Ralf