What is the build of DSSv6 that you are using now ? try a different build ( newer / older ) and try a different ISO file ( try to download a different ISO file and try to check it with .MD5 sum file to be sure that it's downloaded fine), and check the certificate, and create a new one if needed, for that, please check the following KB: http://kb.open-e.com/Create-a-new-certificate_148.html
If you are installing DSSv6 on a USB flash memory, then please be sure that you format it as FAT or FAT 32, and it's recommended if you used a flash memory with size of 1 or 2 GB.
Also try to run the DSSv6 you have on another machine ( for ex your laptop or personal PC ) and see if the GUI works or not.