Hold shift while booting up if grub menu doesn't appear automatically, once you're in the grub menu, press E while you are selecting Ubuntu. Add
nomodeset after quiet splash in the line which starts with
linux. This will disable the graphic drivers which I believe is the problem here. Once you boot up, in order to permanently change your grub options, open a terminal and write:
sudo leafpad /etc/default/grub
leafpad for whatever text editor you use, might be
Search for the line:
Change it to:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset"
Head to a terminal and type
As your question is not a 100% clear and I don't know if you have a dedicated GPU, I believe this is a graphic driver error, so my solution relies on disabling them. However you could just enter Ubuntu using the solution given, then instead of editing grub, simply install your propietary drivers.