Try booting into command line mode by picking the vector-cli or Vectorlinux-cli option from the boot prompt or by selecting the regular default entry, hit the tab key, and then type a "2" (no quotes" at the end of the line.
If you can't do that, boot it normally, then when it gets stuck, press ctrl+alt+F2 simultaneously. That would give you a text login prompt. Log in as user root and enter the root password, then execute this command
that will kill any attempts to start X and give you a plain text system.
Once you're there, execute
It might hang on you... that's ok.. just press CTRL+ALT+backspace
Post any errors you see on the screen after that here.