X and Fluxbox :: resolution don´t realy change

Thanks for answering! The configuration shows: "xvesa -mouse /dev/psawx,5 -screen 800x600x24 -shadow -nolisten tcp2 -I &>/dev/null"
After trying to change System "XVESA" to 1024x768x24 ends in getting no desktop. I have to do "strg/alt/entf" and then "xsetup.sh" to change back to 800x600x24 and then reboot.
Regards

original here.