hi spider79, you can try to press pwr button for long time - tablet goes to off, then you have to plug usb cable to both pc and tablet and then press vol+ and pwr button - pc will make a sound, the screen of the tablet  will be black - it is a recovery mode, now you will be able to find your device in computer devices (install appropriate driver), you can use the RKbatchtool now. If you press pwr+ and pwr without usb connected, you get only dead android on the screen, it works only after instal cwm - then you get cwm menu.

And now I have one question, is here somebody, who has cube u23 gt update.zip file for cwm flash from sdcard, or knows from where to download it?