Hi,
please give us some technical data :
used version of GParted ; system on which is was used (laptop or not, manufacturer / provider , processor, ramsize, graphic card, operation system; special features, one should know, concerning HDD storage configuration or else ).
Generally, it looks like a problem of the graphic system. Did you try to return (from your blackscreen) to console with "Ctrl-Alt-Backspace" and/or use "Forcevideo vesa" on command line or choose vesa-mode from (syslinux-)startmenu ? If you saw the scrolling console messages on installation , 800 x 600 resolution was already working. Every now and then the graphic system fails to switch correctly to the desktop, give it one or two new trials then ... and it works finally; that is my experience with the last three distributions of "GParted Live".
bye
cmdr