So either I need to force it back with a static number, which works, or somehow use a variable setting instead, which I don't know how to do.
blank=`gconftool-2 -g /system/osso/dsm/display/display_blank_timeout` gconftool-2 -t int -s /system/osso/dsm/display/display_blank_timeout 300 gconftool-2 -t int -s /system/osso/dsm/display/display_blank_timeout $blank